As a child, his parents moved the family to New York, and he was educated at the Homer Academy in Cortland County.

[1] He brought his volunteers to Camp Sigel, in Milwaukee, where they were enrolled as Company D in the 27th Wisconsin Infantry Regiment.

After the fall of Vicksburg, they were assigned to VII Corps (Department of Arkansas) and participated in the "Little Rock campaign" under General Frederick Steele.

They subsequently joined Steele's detachment in the Camden Expedition through southern Arkansas, in coordination with the simultaneous Red River campaign in Louisiana.

[3] Concurrent with his service in the Senate, he was elected chairman of the Democratic Party of Wisconsin in 1877, and served in that role for 1878 and 1879.

[3] In 1882, Rankin participated in the redistricting process and was accused of drawing the new 5th congressional district to favor his own election to that seat.

[2] Shortly after arriving in Congress, however, Rankin began suffering from a long illness, which would eventually result in his death.