Business Loop I-25 in Casper is a 2.1 mile long route that serves downtown Casper. It is rarely shown on most street maps of Casper.
For motorists traveling northbound, Business Loop I-25 and its companion, U.S. 87 Business depart Interstate 25/U.S. 20-26-87 at a complex interchange (Exit 186). Although signed as north and westbound, the business route actually travels south on Beverly Street until reaching E Yellowstone Highway, which is U.S. 20-26 Business. The four business routes proceed southwest along Yellowstone Highway until an angled intersection with First Street. Beyond this intersection, the four routes shift onto First Street into Downtown Casper.
Within Downtown at the intersection with Center Street (former WY 255), Business Loop I-25 and U.S. 87 Business turn north onto Center Street, which is maintained by the city of Casper. The pair end at Exit 188 A, where they again meet Interstate 25. The northbound business route utilizes the F Street service road to reconnect with I-25 at the Poplar Street (WY 220) on-ramp.
As an aside, U.S. 20-26 Business continue west along First Street, which eventually becomes known as W Yellowstone Highway. Notably, at the junction between U.S. 20-26 Business, U.S. 20-26 Bypass, and WY 257 (W Casper Belt Loop), some trailblazer shields remain for Business Loop I-25 along westbound U.S. 20-26 Business.
Traveling southbound, the business route is almost identical to the northbound route, with the exception of the south end. Rather than utilizing any portion of Beverly Street, signage for southbound Business Loop I-25 and U.S. 87 Business points to a direct ramp leading from eastbound Yellowstone Highway onto Interstate 25 south. This entrance ramp is just west of the Wyoming Boulevard (WY 258) interchange (Exit 185). It is at this point where mainline U.S. 20-26-87 proceed east along Yellowstone Highway toward the Sinclair Oil Refinery and eventually toward the city of Glenrock.
Business Loop I-25 in Casper is thoroughly signed, but as sometimes occurs along Interstate business routes in Wyoming, erroneous tri-color Interstate shields (without a “To” banner) are posted at multiple locations along the route as of August 2016.