The southernmost Business US-81 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.
Business U.S. 81 was divided in San Antonio on the north side & south side. The north side began downtown along Broadway, then made a right over on Austin Highway. The northern sectioned ended @ JCT I-410 & I-35. It's replaced by Loop 368.
The south side also began outside downtown San Antonio along Nogalitos street. Then made a right along Laredo Highway where it would meet up with I-35. This route is rplaced by Loop 353 & the street was renamed New Laredo Highway.
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 four-mile (6 km) concurrency with K-4, which turns to the west in south Lindsborg. As of October 2012, Business 81 ended at this junction. Prior to this, it went for another mile south before turning east on Smoky Valley Road, ending three miles (5 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 appeared in 1970, at the same time as the McPherson loop.