Yes... Aldrean33's find is an 1851-to-1871 kepi (hat) insignia for US army Infantrymen.
No offense meant, Matt ...but the one in your photo is a Bannermann-era (or later) reproduction. All of the civil war period Kepi (hat) insignia for Enlisted-men's ranks had brass wire loops for attachment to the hat. When you see a simple "straight" iron wire for attachment on a "civil war" Enlisted-man's kepi insignia, it's a Bannerman-era or modernday reproduction. Sidenote: the Model-1872 kepi-insignia had straight brass wires.
That being said, please note that I specified the Enlisted-man's ranks (private, corporal, sargeant) version. The "false-embroidered" version for civil war era Officers had straight brass wire instead of loops.
Here are photos of the Enlisted-man's civil war era version, which always had brass wire loops.