Both of his grandfathers served under Nathanael Greene in the American Revolutionary War and saw military action during the Battle of Guilford Court House.
Shelley worked for John Motley Morehead from 1836 to 1838 in Leaksville, North Carolina, and was later a partner of P. S. Hamlin's tobacco manufacturing business.
Shelley subsequently moved to Calloway County, Kentucky, to continue his business pursuits and serve as justice of the peace.
As a Keokuk resident, he became a wholesaler of dry goods, an investor in real estate, and president of the Iowa Life Insurance Company.
Shelley began his political career affiliated with Henry Clay's Whig Party.