His grandfather, James Caldwell, emigrated from northern Ireland with his family and in 1770 settled in the near-wilderness that became Ohio County.
With Ebenezer Zane, he helped found the town of Wheeling on the Ohio River, becoming a justice of the peace in 1777 and militia commander during the American Revolutionary War, as well as raising a large family.
Bolton Caldwell then went to Harvard University and studied law under Joseph Story and Greenleaf, as his cousin Alfred would soon also emulate.
A. Bolton Caldwell became the United States Attorney for the Western District of Virginia after nomination by President Abraham Lincoln and the concurrence of the U.S. Senate, serving from 1861 until 1863.
After his term as Attorney General Bolton Caldwell won election as Ohio County Prosecutor and later Circuit Judge.