Featured in this book are the Civil War Union army colonels who commanded regiments from Illinois, Iowa, Minnesota and Wisconsin. This is the sixth volume in a series documenting the Union army colonels who did not advance beyond the rank of colonel. A brief biographical sketch of each colonel is included, providing a synopsis of each colonel's Civil War service followed by pertinent details of their life history. Accompanying the biographical sketches are photographs of most of the colonels, many of them published for the first time. Preceding the biographical sketches for each state is a roster of that state's colonels, in regimental order, including those promoted to brigadier general or brevet brigadier general, whose lives are documented in other reference works. Finally, a bibliography of reference sources allows for examination of the lives of the colonels in more detail.