Loop 353 is the former routing of US 81 in southern San Antonio, formed in late 1961 when US 81 was rerouted onto the freeway to the east. When first designated, Loop 353 was marked as a business route of US 81.
Loop 368 is the former routing of US 81 in northern San Antonio, former in late 1962 when US 81 was rerouted onto the freeway to the east. When first designated, Loop 368 was marked as a business route of US 81.
The southernmost Business US-81 in Oklahoma is in the town of Rush Springs, Oklahoma. It begins south of the town, following Rush Street into the central business district. In the middle of downtown Rush Springs, there is a four way stop with Blakeley Avenue. Blakeley carries Oklahoma State Highway 17, which has its eastern terminus at Business US-81. The business route continues north on Rush Street before angling to the northwest to rejoin mainline US-81.
Business US-81 in Rush Springs is signed with a US-81 shield with a small "B" appended after the number. This method of signing business routes is unusual for Oklahoma.
Business US-81 was originally part of mainline US-81. On May 10, 1971, US-81 was relocated to run west of town, and Business US-81 was designated along the old alignment.
Former Business US-81 in Lindsborg began at the intersection of Interstate 135, US-81, and K-4 north of Lindsborg on an older routing of US-81. It shared a 4 miles (6.4 km) concurrency with K-4, which turns to the west in south Lindsborg. At this junction, it went for another mile south before turning east on Smoky Valley Road, ending 3 miles (4.8 km) later at I-135 and US-81. This BUS US-81 had a total length of 8 miles (13 km).
The Lindsborg business loop first appeared in 1970, at the same time as the McPherson loop.