On August 23, 1861, the USS Jacob Bell is mentioned in one source as engaging a Confederate battery at Potomac Creek on the Potomac River.
USS Jacob Bell (1842). Sidewheel steamer, 141 feet long, 21 foot beam, 8 foot hold, one 32-pdr, one 8-inch Dahlgren smoothbore. Built 1842 by Brown & Bell of New York City. Purchased by the Navy 22 August 1861 and commissioned the same day under Lr. Edward P. McCrea.
this was definitely a rush job. Being built in 1842, the ship was also one of the oldest purchased by the Navy.
It was immediately sent to the Potomac River where it joined the steamship USS Ice Boat in shelling the Confedeertae Battery at the mouth of Potomac Creek the next day.
I have to wonder about a ship named the Ice Boat being in the Union Navy, so will have to find out more information about it.