The first USS Union was a steamer designed and constructed by the U.S. Navy as an experimental improved version of its current steam-powered ships which were not considered as efficient as they should be.

The Navy tested various designs of propulsion machinery during the transition to steam power in the early 19th century.

She stopped at Washington, D.C., Boston, Massachusetts, New York City, and Philadelphia, Pennsylvania, before returning to Norfolk in June.

Although both Lt. Hunter and Secretary of the Navy Abel P. Upshur highly praised the vessel, it was later discovered that her engines wasted too much energy uselessly driving the paddle wheels through the water-filled cofferdam inside the ship.

Union joined the Home Squadron in 1844 and conducted a second series of test runs ending in early 1845.