The USS Signal was a small 190 ton steamship which the Navy outfitted as a gunboat. There is no record of when she was commissioned, but it is known that the Signal was in operation October 22nd 1862. She departed on that date from Carondelet, Missouri as part of the campaign against Confederate held Vicksburg. On November 29th 1862 the Signal entered the Yazoo River on a reconnaissance expedition. She was fired on from time to time by Confederates on the river bank, but returned that afternoon unscathed.
On January 4th 1863 the Signal started on an expedition up the White River to attack Confederate held Fort Hindman. After a three day long battle the Fort surrendered. The Signal continued up the White River to make reconnaissance on Little Rock, Arkansas. In February the Signal returned to the Yazoo where she probed until the fall of Vicksburg.