Seidel was born December 13, 1864, in the town of Ashland in Schuylkill County, Pennsylvania, the son of ethnic German emigrants from Pomerania.

[4] During his administration the first public works department was established, the first fire and police commission was organized, and a city park system came into being.

Seidel cleaned up the town with strict regulation of bars and the closing of brothels and sporting parlors (modern-day casinos).

During his administration Seidel employed the noted American poet and author Carl Sandburg as his personal secretary.

[9] Despite winning more votes in 1912 than in 1910, Seidel was defeated by Gerhard Bading, local doctor, professor of surgery, and commissioner of health, on a fusion Democratic-Republican ticket.

[9] Freed of his mayoral duties by electoral defeat, Seidel became a logical choice as the Socialist Party's nominee for Vice President of the United States on the ticket with Eugene V. Debs.

He remained a resident of Milwaukee, living on the northwest side of the city, passing his time painting, composing music, creating poetry, and writing his autobiography.

[10] Seidel died in Milwaukee on June 24, 1947, following an illness of several months' duration related to complications from a heart condition.

Seidel's unpublished memoirs reside in Madison at the Wisconsin Historical Society, where they are available to scholars on microfilm.