Question: Naples, Idaho is on which 2571 mile-long highway that runs across the northern US?

Context paragraphs:
Illinois Route 38: Illinois Route 38 is a west–east state highway that runs across northern Illinois.  It runs from U.S. Route 52 (US 52) in downtown Dixon to US 12/US 20/US 45 (Mannheim Road) in Westchester.  This is a distance of 89.28 mi .  It runs concurrently with the Lincoln Highway between Dixon and the junction of Illinois Route 31 in Geneva where it transitions via State Street onto Roosevelt Road at the junction of Kirk Road and continues through the western suburbs to its terminus at the junction of Mannheim Road.  Roosevelt Road continues on an additional 14 miles without a route designation until terminating at US 41 (Lake Shore Drive).

U.S. Route 34 in Iowa: U.S. Highway 34 (US 34) is a United States Highway that runs across the southern third of Iowa.  It begins on a bridge over the Missouri River west of Glenwood and travels east where it meets Interstate 29 (I-29) and US 275.  Through southwestern Iowa, the highway is, for the most part, a two-lane rural road.  Its interchanges with US 59 near Emerson and US 71 near Stanton and Villisca are located away from populated areas.  At Osceola, the highway intersects I-35 and US 69.  Just east of Ottumwa, where the road meets US 63, the road widens four lanes for the remainder of its trek through the state.  At Mount Pleasant, it overlaps US 218 and Iowa 27, the Avenue of the Saints Highway.  From there, the road heads to the southeast where it crosses the Mississippi River on the Great River Bridge at Burlington.

Logatec Karst Field: The Logatec Karst Field or Logatec Polje (] ; Slovene: "Logaško polje" ) is a karst field near Logatec in southwestern Slovenia (the traditional region of Inner Carniola).  Geographically, it corresponds to the floor of the Logatec Basin (Slovene: "Logaška kotlina" ).  It lies at an elevation between 470 m and 490 m and encompasses about 6 km2 of mostly grassy terrain.  Logaščica Creek, a losing stream, runs across the karst field and collects ambient water.  The karst field often flooded in the past, and so land improvement was carried out.  The northern part of the Logatec Karst Field is called the Empty Karst Field ("Pusto polje" ) and the main road from Logatec to Vrhnika runs across it, passing through the linden-lined section known as the Napoleon Avenue ("Napoleonov drevored" ).  The southern part of the karst field is known as the Lower Logatec Karst Field ("Spodnje logaško polje" ), or metonymically as the Logatec Karst Field ("Logaško polje" ).  The A1 Freeway from Ljubljana to Koper passes along the southeast edge of the karst field.

Interstate 280 (Ohio): Interstate 280 (I-280) is a 12.41-mile-long highway that connects I-75 in northeast Toledo, Ohio with I-80/I-90 (part of the Ohio Turnpike) southeast of the city in northeastern Wood County, Ohio.  Built between 1955 and 1959, the route was originally part of the Detroit-Toledo Expressway.  Although first designated in 1959, the highway originally contained several at-grade intersections and other features which left it substandard to the Interstate Highway System until 1990.  Further construction in 2007 built a new crossing of the Maumee River, replacing an outdated drawbridge.  The highway serves an easterly bypass of metropolitan Toledo, passing through the communities of Northwood and Oregon.  It is one of two auxiliary Interstate highways serving Toledo, the other being Interstate 475.

U.S. Route 2: U.S. Route 2 or U.S. Highway 2 (US 2) is an east–west U.S. Highway spanning 2571 mi across the northern continental United States.  US 2 consists of two segments connected by various roadways in southern Canada.  Unlike some routes, which are disconnected into segments because of encroaching Interstate Highways, the two portions of US 2 were designed to be separate in the original 1926 highway plan.

Naples, Idaho: Naples is a small unincorporated community in Boundary County, Idaho, United States.  It lies 11 miles (18 km) south of the city of Bonners Ferry and 23 miles north of Sandpoint, on U.S. Routes 2/95 in the Rocky Mountains.

M-72 (Michigan highway): M-72 is a state trunkline highway in the US state of Michigan, running from Lake Huron to Lake Michigan across the northern part of the Lower Peninsula.  The highway connects M-22 in Empire with US Highway 23 (US 23) in Harrisville.  It is one of only three Michigan state trunklines that cross the Lower Peninsula, shore to shore.  In between, M-72 runs across Northern Michigan woodland, agricultural areas of the Leelanau Peninsula near Traverse City, and the Au Sable River watershed.  The trunkline also provides access to Camp Grayling, a National Guard training facility near the city of the same name.  Traffic levels along the highway vary from approximately 800 vehicles a day on the east end to over 32,000 vehicles near Traverse City.

U.S. Route 20 in Iowa: U.S. Highway 20 in Iowa is a major east–west artery which runs across the state, separating the northern third of Iowa from the southern two-thirds.  It enters Iowa from Nebraska, concurrent with Interstate 129 and U.S Route 75, crossing the Missouri River at Sioux City.  US 20 runs in a more-or-less straight line across Iowa, paralleling 42° 27' N.  It leaves Iowa in Dubuque by crossing the Mississippi River into Illinois.  The state of Iowa is in the process of upgrading US 20 into a four-lane divided highway for its entire length in Iowa.

Arkansas Highway 60: Arkansas Highway 60 (AR 60, Ark. 60, Hwy.  60) is a state highway that exists in five separate sections in Arkansas.  The longest and most well-known segment of 54.19 mi runs from Highway 28 in Plainview east to U.S. Route 65B (US 65B) in Conway.  A segment in western Logan County of 2.64 mi begins at the Old Highway 10 at the Sebastian County line and runs east to Highway 10.  A third segment of 10.80 mi begins at Highway 252 near Lavaca and runs east to Highway 41 at Peter Pender.  A fourth segment runs 1.34 mi from US 64 and runs across Interstate 40/Interstate 540 (I-40/I-540) to Highway 282.  A fifth route of 2.34 mi begins at Highway 282 near Rudy and runs north to County Road 23 (CR 23).

Colorado State Highway 257: State Highway 257 is an 18.478-mile-long highway in Colorado's Front Range.  It is located entirely in Weld County.  Its western end is at SH 60 and its eastern end is at SH 14.

Supporting paragraphs: Naples, Idaho U.S. Route 2
Answer: U.S. Route 2