Samuel Jordan Kirkwood was born in 1813 in Harford County, Maryland. After early schooling at an academy in Washington, D.C., and a brief career as a drugstore clerk, Kirkwood moved with his family moved to Richland County, Ohio, where he worked as a teacher and a deputy county assessor. Kirkwood read for the law and was admitted to the Ohio bar in 1843; two years later he served as prosecuting attorney for Richland County. After a two-year stint, Kirkwood became a member of the 1850-1851 state convention that drafted the Ohio constitution. In 1855, he left Ohio for Iowa, where he became a miller and a farmer. In 1856, he joined the Iowa Republican Party and was elected to the Iowa state senate.

Two years later, he was serving as director of the State Bank of Iowa, a post he held before becoming governor of the state in 1859 (1859-1864). In 1866, Kirkwood assumed the Senate seat of James Harlan, who had resigned to become President Andrew Johnson's secretary of the interior. Kirkwood served only one year, however, as Harlan wanted his seat back after resigning his cabinet position. In 1875, Kirkwood was again serving as governor, but in 1877 he was reelected as a United States Senator. He did not fulfill his full term, as President Garfield tapped him in 1881 to become secretary of the interior. As secretary, Kirkwood tried to reform the Indian Bureau but had little time to effect major change; President Garfield was assassinated in 1881, and Kirkwood left his post in April 1882. Samuel Jordan Kirkwood returned to Iowa, launched an unsuccessful campaign to become a United States Representative in 1886, and died in 1894.