Instruct: Given a question, retrieve relevant documents that answer the question.
Query: What's the longest highway in the US?
U.S. Highway 20 (US20) is an east–west United States highway that stretches from the Pacific Northwest all the way to New England. The "0" in its route number indicates that US20 is a coast-to-coast route. Spanning 3,365 miles (5,415km), it is the longest road in the United States,[1] and particularly from Newport, Oregon to Boston, Massachusetts, the route is roughly parallel to that of the newer Interstate 90 (I-90), which is in turn the longest Interstate Highway in the U.S. There is a discontinuity in the official designation of US20 through Yellowstone National Park, with unnumbered roads used to traverse the park.
Arkansas Highway 365 (AR 365 and Hwy. 365) is a north–south state highway in Central Arkansas. The route of runs from US 65B/US 79B in Pine Bluff north through Little Rock to US 65B/AR 60 in Conway. The route is a redesignation of former U.S. Route 65, which has since been rerouted onto various Interstate highways through the area. Portions of Highway 365 in Jefferson County are former alignments of the Dollarway Road, which was the longest paved concrete road upon completion in 1913.
Augusta Highway is the longest section of SC 61 from US 17A to the westernmost end of SC 61 where it merges into US 78.
U.S. Route 6 travels east–west near the north edge of the U.S. state of Pennsylvania from the Ohio state line near Pymatuning Reservoir east to the Mid-Delaware Bridge over the Delaware River into Port Jervis, New York. It is the longest highway segment in the Commonwealth. Most of it is a two-lane rural highway, with some freeway bypasses around larger towns. Except east of Dunmore, where it is paralleled by Interstate 84, it is the main route in its corridor. What is now Interstate 80—the Keystone Shortway—was once planned along the US 6 corridor as a western extension of I-84. The corridor was originally the Roosevelt Highway from Erie, Pennsylvania to Port Jervis, New York, designated Pennsylvania Route 7 in 1924. The PA 7 designation soon disappeared, but as US 6 was extended and relocated, the Roosevelt Highway followed it. The Pennsylvania section of US 6 was renamed the Grand Army of the Republic Highway in 1946; this name was applied to its full transcontinental length by 1953.
Business US Highway 287-P (BUS US 287-P) is a business loop of US Highway 287 in the US state of Texas that serves as main street for Mansfield, downtown Fort Worth and Saginaw. The highway is known as Main Street while in Mansfield, Mansfield Highway while in southern Fort Worth, Kennedale Parkway in Kennedale, Riverside Drive and Rosedale Street in central Fort Worth, Commerce Street in downtown Fort Worth, Main Street in northern Fort Worth, and Saginaw Boulevard in Saginaw. The highway was originally designated on January 14, 1991, to replace a portion of Loop 496, and the old route of US 287 and US 81. The route was then rerouted several times during the 1990s. BUS US 287-P is located almost entirely in Tarrant County, and is mostly located in Fort Worth. The highway is, as of 2010, the longest business route of US 287, while located in Texas. BUS US 287-P is one of the few highways to be designated as a north–south highway.
The longest contiguous highway signed as a Utah State Route is State Route 24 at . However, State Route 30 is longer at when the unsigned concurrencies with I-84, I-15, and US-89 are included. The longest highway of any type in Utah is U.S. Route 89 at . The shortest state route is State Route 231, a connector route in Fairview, though this route is unsigned. The shortest signed route is State Route 103 at long, connecting Hill Air Force Base to I-15 and SR-126.
State Highway 16, or SH 16, is a south–north state highway that runs from Zapata on the Texas-Mexico boundary to U.S. Highway 281 24 miles (38.6 km) south of Wichita Falls. It is the longest state highway in Texas at almost 542 miles, but is only the 9th longest of any highway classification in the state. Before the 1939 renumbering, SH 4 was the longest state highway. 
Highway 18 is a highway in the Canadian province of Saskatchewan. It runs from Highway 13 near Robsart, approximately east of the Alberta border, to the Manitoba border near Gainsborough, where it becomes Highway 3. It passes through three major communities, all in the eastern quarter of Saskatchewan – Estevan, Oxbow, and Carnduff; it also passes north of the west and east blocks of Grasslands National Park. Highway 18 is about long, which is the longest east-west highway and second longest highway in Saskatchewan.
In Michigan, the US Highway System covers about of mainline highways and another of special routes. There are 13 mainline highways and 30 special routes in total, including one business route that is unsigned. Two of the mainline highways in the Upper Peninsula exit the state and re-enter, resulting in two discontinuous segments of highway for each in Michigan. The longest US Highway in the state is US Highway 23 (US 23) at just over spanning from the Ohio state line north to the Straits of Mackinac in the Lower Peninsula, while the shortest is the segment of US 8 south of Norway in Dickinson County. Special routes range in length from about for Business US 2 (Bus. US 2) in Ironwood to for Bus. US 131 in Kalamazoo.
Maryland has 14 U.S. Highways, including seven primary U.S. Highways and seven auxiliary U.S. highways. The longest U.S. highway in Maryland is U.S. Route 40, while the shortest U.S. highway is US 522. Maryland also contains six former U.S. highways.
In the original Louisiana Highway system in use prior to 1955, LA 26 was part of two different routes. The east–west section from DeRidder to Oberlin made up the entirety of State Route 52. The north–south section from Oberlin to Lake Arthur was part of State Route 25, a long U-shaped route that continued east along the present LA 14 to New Iberia then north along LA 31 to Opelousas. Both Routes 25 and 52 were included in the first 98 state highway routes designated by the Louisiana Legislature in 1921 as part of an act which also created the Louisiana Highway Commission, an early forerunner of the Louisiana Department of Transportation and Development (La DOTD). Additionally, the stretch between DeRidder and Elton served briefly as part of US 190 when that highway was extended westward from Baton Rouge in 1935. However, the roadway was still gravel west of Oberlin and dirt from Oberlin to Elton. In the late 1930s, US 190 was shifted twice to take advantage of paved roadways in the area. It was ultimately routed via US 171 from DeRidder south to Ragley and what was then State Route 7 through Kinder, eliminating the longest stretch of the unpaved roadway on US 190 within the state.
The Interstate Highways in Utah are maintained by the Utah Department of Transportation (UDOT). The Interstate Highway System is a nationwide system with only a small portion of these routes entering Utah. Originally, the State Road Commission of Utah, created on March 23, 1909 was responsible for maintenance, but these duties were rolled into the new UDOT in 1975. There are of Interstates within the state. The longest is Interstate 15 (I-15) at and the shortest is I-215 at . One unique former route is Interstate 415, which was never signed as such, and was only used as a temporary designation for the eastern portion of what is now the Interstate 215 belt loop around Salt Lake City.
In the state of Mississippi, there are 14 U.S. highways. The longest is US 49, and the shortest being US 425.
Vermont Route 100 (VT 100) is a north–south state highway in Vermont in the United States. Running through the center of the state, it travels nearly the entire length of Vermont and is long. VT 100 is the state's longest state highway, the longest north-south route in Vermont, and the longest numbered highway in Vermont of any type.
K-4 is the longest designated state highway in Kansas traversing from north of Scott City at US-83 to US-59 near Nortonville in northeast Kansas. A segment of the highway in Saline County overlaps Interstate 135, and a section in Topeka runs concurrent with Interstate 70.
As a former US Highway, the route passes through many historic districts and has many junctions. The route begins at US 65B/US 79B (the Martha Mitchell Expressway) in northwest Pine Bluff near the University of Arkansas at Pine Bluff and runs northwest. Highway 365 is known as Dollarway Road in this part of Pine Bluff as it follows the original routing of the Dollarway Road, a 1913 paving project that gave Jefferson County the longest continuous concrete road in the nation at the time. Highway 365 meets its spur route further northwest, the spur connects Highway 365 to Interstate 530/US 65 and US 270. Now entering White Hall, Highway 365 passes the historic Bellingrath House and intersects Highway 256 near the Pine Bluff Arsenal.
Although the portion of the road from Alburgh to Burlington follows a north-south alignment, US 2 is continuously signed east (heading south during this portion) and west (heading north) to match its overall alignment, making it the longest east-west signed route in the state. At a nearly 460-mile overall length, US 2 is also the longest highway of any designation (Interstate, US Route, or state highway) that enters the state of Vermont.
U.S. Route 6 (US 6), also called the Grand Army of the Republic Highway, honoring the American Civil War veterans association, is a main route of the U.S. Highway system. While it currently runs east-northeast from Bishop, California to Provincetown, Massachusetts, the route has been modified several times. The highway's longest-lasting routing, from 1936 to 1964, had its western terminus at Long Beach, California. During this time, US 6 was the longest highway in the country.
The Interstate Highway System covers about in the state and consists of four primary highways and nine auxiliary highways. There are additional 29 business routes associated with the system in Michigan. The longest segment of Interstate Highway in the state is Interstate 75 (I-75) at just under ; the shortest is I-375 at . The length of I-75, the longest highway of any kind in the state, includes the Mackinac Bridge, which is maintained by the MBA, the only section of state highway not under MDOT jurisdiction. The Mackinac Bridge is one of three monumental bridges in the state used by I-75; the others are the Zilwaukee and International bridges. A fourth, the privately owned Ambassador Bridge connects I-75 and I-96 in Detroit to Canada.
The U.S. Highways in Alabama are the subset of the United States numbered highway system. These highways in the U.S. state of Alabama are maintained by the Alabama Department of Transportation (ALDOT). There are 19 U.S. highways that travels through Alabama, totaling . U.S. Route 31 (US 31) is the highway with the longest segment in Alabama, with . The shortest is US 72 Alternate, crossing of North Alabama. One former U.S. highway existed in Alabama: US 241. It traveled through the eastern part of the state. US 241 was replaced by US 280 and US 431 in 1954.
In anticipation of the formation of the United States Highway System in 1926, the Highway Department commissioned the construction of the Gillespie Dam Bridge, a steel truss bridge just downstream from the dam. The bridge was completed and opened to traffic on August 1, 1927 at a cost of US$320,000 ("US$3,950,000 in 2007"). The bridge, which was at the time the longest highway bridge in the state of Arizona, was immediately incorporated into the highway system as Route 80. The bridge carried US 80 traffic until 1956 when the highway was decommissioned, devolving to a county highway, thus placing the bridge under Maricopa County care. The bridge was added to the National Register of Historic Places on May 5, 1981.
The US Highways in Michigan are the segments of the national United States Numbered Highway System that are owned and maintained by the US state of Michigan, totaling about . The longest of these is US Highway 23 (US 23) at around . On a national level, the standards and numbering for the system are handled by the American Association of State Highway and Transportation Officials (AASHTO), while the highways in Michigan are maintained by the Michigan Department of Transportation (MDOT).
The following is a list of U.S. Highways in Maryland. There are currently 14 U.S. Highways that exist entirely or partially in the U.S. state of Maryland. Seven of these are primary U.S. Highways while seven are auxiliary U.S. Highways that may or may not be related to one of the primary U.S. Highways. The longest primary U.S. Highway in Maryland is U.S. Route 40 (commonly abbreviated US 40) at . The shortest primary U.S. Highway in Maryland is US 11 at . The longest auxiliary U.S. Highway in Maryland is US 301 at . The shortest auxiliary U.S. Highway in Maryland is US 522 at . All U.S. Highways are maintained by the Maryland State Highway Administration except for the portions that run through Baltimore, Hagerstown, and Cumberland. Maryland has five former U.S. Highways; those five are shaded in dark gray in the list.
Business US Route 83-S (Bus. US 83-S) is a business loop of US 83 in the Lower Rio Grande Valley region of Texas. The highway serves as the main street for many communities in the area, such as McAllen, Mission, San Juan, Alamo, and more.
This is the longest business loop in Texas, traveling almost 47 miles and is the third longest bannered US highway in the state; only US 90 Alternate and US 77 Alternate are longer.
Unlike most Interstate Highways, much of I-70 in Utah was not constructed parallel to or on top of an existing U.S. Highway. Portions of I-70 were constructed in areas where previously there were no paved roads. Because it was built over an entirely new route, I-70 has many features that are unique in the Interstate Highway System. For example, the between Green River and Salina makes up the longest distance anywhere in the Interstate Highway System with no motorist services. This same piece is noted as the longest highway in the United States built over a completely new route since the Alaska Highway, and the longest piece of Interstate Highway to open at a given time. The construction of the Utah portion of I-70 is listed as one of the engineering marvels of the Interstate Highway System.