Company "B" organized at Paris, Edgar County, Ill., and mustered in at St. Louis August 5, 1861.

Company "C" organized at Prairie City, Ill., and mustered in at St. Louis August 19.

Company "G" organized at Cape Girardeau, Mo., and mustered in on September 17, 1861.

Company "I" organized in Iowa and mustered in on October 31, 1861, at St. Louis, Mo.

Company "K" organized at Burlington, Iowa, and mustered in at St. Louis, Mo., October 31, 1861.

Engineer Brigade, District of West Tennessee, Dept.

Companies "A" and "B" ordered to East St. Louis, Mo., August 6, 1861; thence to Cape Girardeau, Mo., August 6–7, and fatigue duty there until March, 1862, when rejoined Regiment at New Madrid, Mo.

Regiment moved from St. Louis, Mo., to Lamine Bridge, on Missouri Pacific Railroad, September 19, 1861, and duty there until October 26.

Grant's Central Mississippi Campaign November, 1862, to January, 1863.

Moved to Young's Point, La., February 11–14, thence to Lake Providence, La.

Engineer operations at Baxter's Bayou and Bayou Macon constructing Batteries at Young's Point, and various expeditions to explore and open Bayous until April, 1863.

Engaged in opening Memphis & Charleston Railroad to Corinth, Miss., then at Pocahontas May 11 to October 3.

Repairing Memphis & Charleston Railroad east of Corinth, Miss., October 3–28.

Moved to Milliken's Bend May 9; duty there and at Young's Point and Chickasaw Bayou until May 25.