Blair was born in Caroline, New York, in a log cabin built by his father George Blair. Until he was 17 years old he helped his father at the farm in Oswego, New York in Tioga County, New York of Eaton County in 1842.
He moved back to Jackson in 1844 and was a Whig member of the Michigan State House of Representatives from Jackson County from 1846 to 1849. He served on the House Judiciary Committee. He also introduced legislation to allow black citizens the right to vote.
n February 1849, Blair married Sarah L. Ford. Together they had four sons. He was elected Jackson County prosecutor in 1852 and participated in organizing the Republican Party in 1854.He served in the Michigan Senate from 1855 to 1856.He was also elected Governor of Michigan in that year and reelected in 1862, serving from 1861 to 1865.
He served as Civil War Governer.
He died in Jackson and is interred at Mt. Evergreen Cemetery there.