Blair was born at Abingdon, Virginia on April 12, 1791. He moved to Kentucky and later graduated from Transylvania University in 1811. Blair became a journalist in Frankfort, Kentucky and Washington D.C., and a prominent leader of the Democrats. He was married to Eliza Violet Gist from 1812 until his death in 1876. They had five children. He founded Silver Spring, the second largest city in Maryland, in 1840.