It begins at Interstate 15 (I-15) exit 118 on West Broadway Street and runs concurrent with the I-15 Bus.

Curving under a set of railroad bridges, the street name briefly changes to the Northgate Mile.

in St. Anthony, Idaho, begins at exit 346 on US 20 and proceeds northward onto Bridge Avenue.

After crossing Henrys Fork, the route enters the St. Anthony downtown area.

continues to the east, crossing Henrys Fork again, before bending to the southwest and ending at an intersection with mainline US 20.

follows US 20's old alignment through South Sioux City before crossing into Iowa concurrently with US 77.

then joins with I-29 for a very short distance before exiting onto Virginia Street and then Gordon Drive.

The route then follows Gordon Drive through central Sioux City to the US 20/US 75 bypass, where it rejoins US 20.

in Fort Dodge, Iowa, begins at the western end of the current US 20 expressway near Moorland and follows US 20's former route through the city via Kenyon Road and 5th Avenue South.

turns south on Webster County Road P59 (CR P59), passing through several gypsum mining areas before rejoining the US 20 expressway in Coalville.

[3] The former routing that ran through downtown Freeport along Galena Avenue and South Street became US 20 Bus.

Through downtown, westbound traffic followed Center Street for one block to take Highland Avenue across the Fox River.

At Harlem Avenue, it turned south to continue east on Washington Boulevard.

Initially, opposing traffic traveled together on Washington Boulevard from Union Park to the South Branch Chicago River where it followed Wacker Drive to Michigan Avenue.

The route followed both streets to Michigan Avenue for four years before returning to Wacker Drive.

The original route took 16th Street one block east to Indiana Avenue and thence to Cermak Road.

The route followed Cermak Road to a short diagonal named Silverton Way to South Parkway (now Martin Luther King Drive).

follows the former route of US 20 through South Bend and Mishawaka, Indiana, generally along Colfax Avenune and McKinley Avenue/McKinley Highway.

When the freeway was completed to the east reconnecting to US 20, the mainline US 20 designation was transferred to it, rather than the US 20 Byp.

from their common eastern terminus in the Ohio City neighborhood in Cleveland to US 20/State Route 113 (SR 113) in Rocky River from 1971 to 1983.

The road begins at an intersection with US 20 in Silver Creek, goes along Central Avenue for a short time and merges in with NY 5.