M-139 was designated as a state trunkline by 1931 from US 31 at
Scottdale to
US 12 in Benton Harbor. In late 1953 or early 1954 M-139 was extended westward along US 12 and then northward along Paw Paw Avenue to meet a new bypass routing of US 31 north of Benton Harbor. US 31 was rerouted to follow what is now the
I-196 freeway in 1963. At that time, US 31 was then routed along I-94 and M-139 to Scottdale. The following year, the
concurrency was removed when M-139 was truncated to end at I-94/US 31. The northern extension on Paw Paw Avenue was turned back to local control, truncating the northern end of M-139 to the intersection with BL I-94 (previously US 12). Plans for M-139 to be extended on a new east-west facility north of downtown Benton Harbor were halted in 1965 when the city and the state disagreed on how best to traverse a railroad; the project had been canceled by February 21, 1966. On August 27, 2003, the
St. Joseph Valley Parkway freeway carrying US 31 was completed from northwest of Berrien Springs (exit 15) to Napier Avenue near Benton Harbor (exit 24). The former section of M-139 replaced by US 31 was once again designated M-139, with M-139 extending further along the former US 31 to the freeway's exit 15. In 2008, M-139 was planned to extend southerly to end at Main Street (
Business US 12, Bus. US 12) in Niles along the unsigned state trunkline OLD US 31 and
Bus. US 31, but after the City of Niles announced its plan to take over maintenance of the section of East Main Street between Front Street/Bus. US 31 and Fifth Street/
M-51 in order to ban trucks, the plan was revised to extend M-139 further south, replacing the Bus. US 12 designation southwesterly to US 12. The extension was executed on March 5, 2010, prior to route marker installation. ==Major intersections==