Pingree added to the old stock Yankee Republican base by making large inroads into the German and Canadian elements.

Warning repeatedly against the dangers of monopolistic corporations, he launched nationally visible crusades against Detroit's streetcar, gas, electric, and telephone companies.

As governor, he succeeded in forcing passage of the nation's first major statewide reappraisal of railroad and corporate property, with intent on implementing taxes.

[3] In 1862, Pingree enlisted in the Union Army to serve in the Civil War with the 1st Massachusetts Heavy Artillery Regiment (Company F).

He fought with the Second Brigade of Tyler's Division, Second Corps, which participated in battles at Fredericksburg Road (May 18), Harris Farm (May 19), and Spotsylvania Court House (May 19–21).

[3] His regiment was then assigned to the Second Corps, Third Division, in the Army of the Potomac and fought at North Anna (May 24–25) where he and some other men were captured by a detachment of John S. Mosby's command.

Pingree rejoined his regiment, fought in many more battles, and was present at Appomattox Court House when Robert E. Lee surrendered on April 9, 1865.

[3] Pingree was a cobbler by trade and, following the war, moved to Detroit and briefly worked for Henry Porter Baldwin's shoe company.

[5] His largest struggle, however, was with Tom L. Johnson, president of the Detroit City Railway, over lowering streetcar fares to three cents.

[7] When the company sought a thirty-year contract with the city, Pingree opposed it, leading a major shareholder, James McMillan, to express vehement disapproval.

He gained national recognition through his "potato patch plan", which allowed poor people to use 430 acres (170 ha)[8] of vacant city land for growing food.

[7] A 1993 survey of historians, political scientists and urban experts conducted by Melvin G. Holli of the University of Illinois at Chicago saw Pingree ranked as the fourth-best mayor of a major American city to serve between the years 1820 and 1993.

[5] During his four years in office, Pingree promoted the regulation of railroad rates, equal taxation, and municipal ownership of public utilities.