On May 19, 1846, following the initial battle between Mexican forces and United States troops under Gen. Zachary Taylor in the disputed territory between the Neuces and Rio Grande rivers, Michigan's Governor received a request from the War Department to enroll a regiment of volunteer infantry. Made up of 10 companies, the regiment would be held in readiness for service until called for by the President.
Under the first call, 13 independent companies, 11 infantry and two cavalry, responded. However, only Detroit's Brady Guards were accepted. The men were sent to garrison the posts at Mackinac and Sault Ste. Marie to free the regular troops stationed there for duty in Mexico. Of the companies tendered for service, four were from Detroit, two from Monroe, three from Lenawee County, and one each came from St. Clair, Hillsdale, Berrien, and Wayne County (outside Detroit).
The First Michigan Volunteers was enrolled and mustered in answer to a second call in October 1847. The companies were from: Kalamazoo, St. Clair and Wayne Counties, Pontiac, three from Detroit, western Michigan, Hillsdale, Lenawee, Monroe, Marshall, and the southeastern part of the state. The companies were mustered into federal service at various times during November and December 1847 and January and February 1848.
Prior to January 1848, six companies were sent to the battle area and landed at Vera Cruz, Mexico, where the four remaining Michigan companies later joined them. General Scott was already occupying Mexico City when the last companies advanced as far as Cordova, which they garrisoned until the peace treaty was signed. Michigan troops guarded General Scott's communications lines.
Although Michigan men were in the field for nearly six months, they never saw battle. The regiment was mustered out at Detroit on July 23, 1848.