US 421 begins at
Fort Fisher, North Carolina, and heads generally to the northwest to
Michigan City, Indiana. Along the way, it passes through
Bristol, Tennessee and
Virginia;
Lexington, Kentucky; and
Indianapolis, Indiana.
North Carolina US 421 begins near
Fort Fisher State Recreation Area and heads through North Carolina's southeastern beaches to
Wilmington. It then heads in a northwesterly direction through
Clinton,
Dunn,
Lillington,
Sanford and
Siler City to the
Piedmont Triad region. Major highway junctions between north of Wilmington and Greensboro are
North Carolina Highway 11 (NC 11),
Interstate 95 (I-95),
US 401,
US 1,
US 64 and
I-85. In Greensboro, it follows the
Greensboro Urban Loop paired with I-85 south of Greensboro, close to Pleasant Garden, and
I-73 northwest of Greensboro, close to Colfax. It then departs the urban loop and connects to
I-40 towards
Forsyth County as it becomes its own freeway along the former Business Loop 40 alignment. Major intersections are
NC 150,
NC 66,
NC 67,
US 158 and
US 52 between Greensboro and
Winston-Salem. After Winston-Salem, it intersects I-40 once again but continues westerly passing through
Lewisville,
Yadkinville,
Wilkesboro and
Boone. Major highway junctions between Winston-Salem and Boone are
US 601,
I-77,
NC 16,
Blue Ridge Parkway,
US 221 and
US 321. US 421 continues westerly into Tennessee towards
Mountain City, Tennessee. US 421 is a limited-access freeway through Siler City northward. US 421 is a divided highway from north of
NC 49 all of the way to
Wilkesboro.
Tennessee US 421 enters Tennessee from North Carolina at
Trade. It is the oldest crossroads community in Tennessee and is the easternmost part of the state. The road "as the crow would fly" is a short distance in Volunteer State but traverses through two mountain ranges. After Trade, it ventures into
Mountain City through a zone while bypassing the downtown area. After Mountain City, begins the two mountain ranges and in between them is the area of
Shady Valley. The two ranges are a popular motorcycle route known as "The Snake". More than 400 curves over an approximately ride. After the second mountain range, it flattens out after the
South Fork Holston River heading towards
Bristol. US 421 enters Virginia on the Old Dominion side of Bristol. Major highway junctions between the NC and VA state lines are
State Route 67 (SR 67) in Mountain City,
SR 91 the new Mountain City bypass,
SR-394, and
US 11E.
Virginia US 421 enters from Tennessee in
Bristol and goes west to
Weber City,
Duffield, and
Pennington Gap in Southwest Virginia. The route goes through the Cumberland and Powell Mountains, and goes by
Natural Tunnel State Park near Duffield.
Kentucky US 421 enters the Bluegrass State running from the Pennington Gap area in Virginia into
Harlan County. For the distance between the Virginia state line and closer to
Hal Rogers Parkway, it is a major north–south two-lane highway. However, its passing zones are largely limited to a stretch after the Virginia line, through Harlan and along
US 119. US 421 then crosses Pine Mountain and enters
Leslie County, turning west at
Hyden and paralleling the Hal Rogers Parkway. Between
Manchester and
McKee, US 421 functions as more of a local road with many curves. The roadway improves as it descends from the Cumberland Plateau into the Bluegrass Region at Big Hill in
Madison County near
Berea. It joins
US 25 at the Blue Grass Army Depot south of
Richmond and roughly parallels
I-75 towards
Lexington. Through Lexington, it is Richmond Road, Main Street and Leestown Road. The segment between Lexington and Frankfort was once designated
Kentucky Route 50 (KY 50).
US 62 runs briefly with US 421 in this section. In
Frankfort, US 421 runs with US 60 on the west side of town, then runs within the city's northern bypass, briefly joining
US 127. US 421 then traverses the very hilly area of northwest
Franklin County, around the
Flag Fork community. It then runs through
Henry and
Trimble counties, exiting the state at
Milton, crossing the
Ohio River into
Madison, Indiana via the
Milton–Madison Bridge.
Indiana US 421 winds through the southern part of Indiana as it runs from Madison, in the southeastern part of the state, to
Indianapolis. North of
Greensburg, US 421 intersects and merges with
I-74 west, through the
Shelbyville area en route to Indianapolis. Originally, US 421 followed Southeastern Avenue into downtown Indianapolis, where it merged with US 40 (
Washington Street) to West Street, then turned north, following West Street, Northwestern Avenue (later MLK Street), and Michigan Road up to the northwest side of the city. US 421 went past the Pyramids, an Indianapolis landmark. North of
Indianapolis, US 421 continues to the north-northwest, providing a direct highway link between Indianapolis and
Michigan City. US 421 ends at its junction with
US 20 on the south side of Michigan City. Originally, the highway's end was a few miles north at the junction with
US 12 near the shores of Lake Michigan. ==History==