The Fourth Wisconsin Cavalry was organized as the 4th Wisconsin Infantry Regiment at Camp Utley, Racine, WI, and mustered into the service of the United States on the July 2nd, 1861. It left the state on the 15th of July, proceeding to Baltimore, MD, and into camp at the Relay House, MD, August 5, 1861, remaining on duty there until early in November when the regiment was transferred to Baltimore. It remained there until the latter part of February, 1862, when it proceeded to Newport News, VA, from which point the Fourth embarked on the 6th of March to join the "Army of the Gulf." It arrived at Ship Island below New Orleans March 12, 1862, and landed in New Orleans on May 1st. It was at once assigned to active service and took part with an expedition up the Mississippi River against Vicksburg in May, and another in June, and with this force occupied Baton Rouge, LA, a little later in the year. The forces there were employed in successful expeditions during that winter, and in May were collected with a view of capturing Port Hudson, LA, in which siege and sanguinary contest the Fourth participated May 21 to July 8,1863. This was the last service of the Fourth as a regiment of Infantry.
On the 1st of September, 1863, the regiment was by order of the War Department equipped as a cavalry regiment. Thereafter the Fourth regiment was actively and almost constantly engaged in scouting, picketing and accompanying expeditions of various points in Louisiana and Mississippi until July, 1865, when with other troops it was transferred to Texas near the Rio Grande. Companies of the regiment were detached to guard different points along the line of that river, and the whole command remained in this service until the latter part of May, 1866, when the regiment was transferred to Madison, WI, which place was reached June 14th and the regiment was soon thereafter mustered out of service of the United States and disbanded.
The histories above, unless otherwise noted, are adopted from Charles E. Estabrook, ed., Records and Sketches of Military Organizations, (Madison, 1914).