In Mason County, US 377 passes through Streeter before forming a concurrency with SH 29 near Grit.

In Mason, SH 29 splits off to its own alignment while US 377 turns north to join U.S. Route 87.

US 377 splits off to the north and heads to Mercury and crosses the Colorado River near Winchell.

At the Interstate 35W junction, it heads north along that highway before splitting off at Exit 52A (Belknap St.).

It heads due north at the Denton Highway and continues to run parallel to I-35W through many Fort Worth suburbs, including Haltom City, Watauga, Keller, Westlake, Roanoke, and Argyle.

It continues through Aubrey, through Pilot Point, Tioga, and Collinsville, before having an interchange with US 82 at Whitesboro.

US 377/SH-99 run north from Tishomingo, having a one-mile (1.6 km) three-route concurrency with SH-7 before meeting State Highway 3 southeast of Ada.

[1] US 377 long remained a two-lane highway between Denton and Fort Worth, but has since been widened with more construction scheduled.

[4] On June 18, 1964, AASHO accepted an extension of US 377 from the Texas state line, but only 17 miles (25 km) to US 70 in Madill.

[10] By the late 2010s, it had guardrail damage causing the remaining bridge to be very narrow and was considered structurally deficient.

[11][12][13] An original estimated start for replacement bridge was February 2018, costing $80 million.

[15][16] The project, originally planned to be opened to traffic in 2022, has faced multiple delays.

The loop is just 0.209 miles (0.336 km) long, and is located entirely within the downtown portion of the town of Roanoke, Texas.

The original route traveled from US 377 just south of Roanoke, along Oak Street, past Bus.

[21] On September 26, 1996, the stretch of Oak Street traveling from US 377 to Denton Drive was given back to the city of Roanoke.