Robert McClelland was born in Greencastle, Pennsylvania on August 1, 1807, the son of a prominent Franklin County doctor, John McClelland, and his wife, Eleanor Bell McCulloh. The father had studied medicine under Benjamin Rush and perhaps not coincidentally the younger McClelland entered Dickinson College in Carlisle, Pennsylvania to graduate high in the Class of 1829.
McClelland was admitted to the Pennsylvania bar in 1832 in Chambersburg, and he practiced law in Pittsburgh for a short while before leaving the state for Monroe, Michigan in 1833. He set up a successful law practice and was a member of the convention to prepare Michigan for statehood in 1835. At the same time he became a leader in the new state's Democratic Party. He served as a member of the board of regents of the University of Michigan at Ann Arbor in 1837 and was elected to the state legislature for the first time in 1838. He became speaker of the state house in 1842 and from 1843 represented his district in the U.S. Congress for three terms sitting on the Commerce Committee and the Foreign Relations Committee.
McClelland became, among other things, a strong advocate for states' rights, including the right of a state to permit slavery. His star rose in the party and he represented Michigan in several national conventions. He also was an active member of the constitutional convention in Michigan in 1850 and the chair of the state Democratic Convention that year. In 1851, he was elected governor of Michigan and re-elected by an even greater majority in 1852. Soon after, having noted his active part in his presidential election, President Franklin Pierce named him to the cabinet as Secretary of the Interior. In that position, McClelland advised the president to follow his neutral policy concerning Kansas, but most of his recommendations for reform made little progress. Nonetheless, he built a reputation for organization and honesty in a previously chaotic and corrupt department. After James Buchanan's inauguration in 1857, McClelland retired to a long and successful private practice in Detroit. He sat again in a Michigan state constitutional convention in 1867.
In 1836, he married Sarah Elizabeth Sabine of Williamstown, Massachusetts and the couple had six children. Three of their children reached maturity. Robert McClelland died in Detroit on August 30, 1880.