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.

Source: Wisconsin Veterans Museum

1861

• Guard Railroad near Baltimore, Md., until November, 1861.
• Expedition to eastern shore of Maryland November 14-22.

1862

• Duty at Baltimore until February, 1862.
• Moved to Fortress Monroe, Va., February 19, thence sailed on Steamer "Constitution" for Ship Island, Miss.,
• March 5, arriving there March 13, and duty there until April 16.
• Operations against Forts St. Phillip and Jackson April 16-29.
• Surrender of Fort St. Phillip April 29.
• Occupation of New Orleans May 2.
• Expedition to New Orleans and Jackson Railroad May 8-10.
• Occupation of Baton Rouge May 12.
• Reconnaissance to Warrenton May 14-29.
• At Baton Rouge until June 17.
• Expedition from Baton Rouge June 7-9 (2 Cos.).
• Williams' Expedition to Vicksburg, Miss., and operations in that vicinity June 20-July 26.
• Grand Gulf June 23-24.
• Battle of Baton Rouge, La., August 5.
• Evacuation of Baton Rouge August 20.
• Bayou Des Allemands September 4-5.
• Expedition from Carrollton to St. Charles' Court House September 7-8.
• At Carrollton until September 29 and at Camp Parapet until December 19.

1863

• Bonnet Carre near St. Charles' Court House September 8.
• Moved to Baton Rouge December 19, and duty there until February, 1863.
• Co. "G" detached for Heavy Artillery service in the Defenses of New Orleans November 13, 1862, to August 14, 1863.
• Moved to Bayou Plaquemine February 6, 1863.
• Expedition to Indian Village February 13.
• To New Orleans February 23, thence to Baton Rouge March 6.
• Demonstration on Port Hudson March 7-27.
• Operations in Western Louisiana April 9-May 14.
• Teche Campaign April 11-20.
• Fort Bisland April 12-13.
• Pursuit to Opelousas April 15-20.
• Expedition to Bayou Plaquemine April 22-23.
• Expedition from Opelouses to Chicotsville and Bayou Boeuf April 26-29.
• Near Washington May 1.
• Boyce's Bridge, Cotile Bayou, May 14.
• Cheyneyville May 18.
• March to Port Hudson May 19-25.
• Siege of Port Hudson May 25-June 9.
• Expedition to Niblitt's Bluff May 26-29.
• Assault on Port Hudson June 14.
• Grierson's Expedition to Clinton June 1-6.
• Clinton June 3-4. Surrender of Port Hudson July 9.
• Moved to Baton Rouge, La., July 25, and duty there until September.
• Designation of Regiment changed to 4th Wisconsin Cavalry August 22, 1863 .
• Duty at Baton Rouge engaged in scouting, picketing and operating against guerrillas in that section of country lying between the Comite, Amite and Mississippi Rivers until June, 1864.
• Near Baton Rouge September 8, 1863 (Detachment).
• Greenwell Springs Road September 19 (Detachment), and October 5.

1864

• Donaldsville February 8, 1864.
• New River February 9.
• Expedition to Rosedale February 14-22.
• Baton Rouge March 8.
• Black Bayou March 19.
• Reconnaissance to Clinton May 1.
• Olive Branch Church near Baton Rouge May 3.
• Baton Rouge June 16.
• Plaquemine June 28.
• Ordered to Morganza June 29, and duty there until August 9.
• Plaquemine August 6.
• Moved to Baton Rouge August 9.
• Near Bayou Letsworth August 11.
• Expedition to Clinton August 25-29. Olive Branch, Comite River and Clinton August 25.
• Expedition to Clinton, Greensburg and Camp Moore October 5-9.
• Expedition from Baton Rouge to Brookhaven, Miss., and skirmishes November 14-21.
• Liberty Creek November 15.
• Jackson November 21.
• Davidson Expedition to Mobile & Ohio Railroad and Pascagoula Bay November 27-December 13.

1865

• At Baton Rouge until April, 1865.
• Mobile Campaign April.
• Capture of Mobile April 12.
• March through Alabama to Georgia and to Vicksburg, Miss., April 18-June 5.
• Moved to Shreveport, La., June 26-July 2.
• March to San Antonio, Texas July 8-August 3, and duty there until October.

• Expedition to Fort Inge and to Fort Clark and Eagle Pass September.

1866

• Guard and patrol duty along the Rio Grande from Brownsville to Laredo Until May 1866.
• Mustered out at Brownsville May 28, 1866.
• Moved to Madison, Wis., June 3-18, and discharged June 19, 1866.

Regiment loses during service 11 Officers and 106 Enlisted men killed and mortally wounded 3 Officers and 311 Enlisted men by disease. Total 431.

Source - "A Compendium of the War of the Rebellion" by Frederick H. Dyer (Part 3)