The new "ninety-day gunboat" departed New York 5 February and reached Key West, Florida, 10 days later where Comdr.

[citation needed] The mortar flotilla had been established by the Navy to neutralize forts St. Philip and Jackson which protected New Orleans, Louisiana against attack from the sea.

Owasco was one of seven steamers assigned to the flotilla to tow the schooners and help them navigate safely in the tricky currents of the Mississippi River.

Owasco participated in the bombardment and capture of Galveston, Texas 3 October; but, on New Year’s day, was driven out of that port by Confederates in cotton clad steamers.

[citation needed] This article incorporates text from the public domain Dictionary of American Naval Fighting Ships.