57th Regiment, Enrolled Missouri Militia (Union)
The regiment was enrolled between 28 July 1862 and 9 August 1862. They were first ordered into service between 1 August 1862 and 31 August 1862. They were first discharged between 8 September 1862 and 30 April 1863. They were ordered into service between 11 November 1863 and 18 November 1863. They were discharged between 5 February 1864 and 29 March 1864. They were finally ordered into service between 10 and October 1864. They were finally discharged between 30 and 31 October 1864. The Colonel in charge was Colonel David J. Heaston. 
Companies in this Regiment with the Counties of Origin
Men often enlisted in a company recruited in the counties where they lived though not always. After many battles, companies might be combined because so many men were killed or wounded. However if you are unsure which company your ancestor was in, try the company recruited in his county first.
Company D - Captains William T. Foster, and Jonathan C. Frisby - Many men from Harrison County
Company E - Captain William J. Prater - Many men from Bethany, Harrison County
Company F - Captain Stephen Allen - Many men from Bethany, Harrison County
Company G - Captain Preston Sharp - Many men from Eagleville, Harrison County
Company H - Captains William H. Hillman, and James M. Nevill - Many men from Eagleville, Harrison County
Company I - Captain James H. Linch - Many men from Bethany, Harrison County
Company K - Captain William H. Harper - Many men from Eagleville, Harrison County
Company L - Captains James L. Anderson, and Calvin Tilton - Many men from Eagleville, Harrison County
The above information about the companies with partial rosters is found in Kenneth E. Weant's book, Civil War Records: Missouri Enrolled Militia Infantry Regiments, Volume 8 
- Beginning United States Civil War Research gives steps for finding information about a Civil War soldier or sailor. It covers the major records that should be used. Additional records are described in 'Missouri in the Civil War' and 'United States Civil War, 1861 to 1865' (see below).
- National Park Service, The Civil War Soldiers and Sailors System, is searchable by soldier's name and state. It contains basic facts about soldiers on both sides of the Civil War, a list of regiments, descriptions of significant battles, sources of the information, and suggestions for where to find additional information.
- Missouri in the Civil War describes many Confederate and Union sources, specifically for Missouri, and how to find them.. These include compiled service records, pension records, rosters, cemetery records, Internet databases, published books, etc.
- United States Civil War, 1861 to 1865 describes and explains United States and Confederate States records, rather than state records, and how to find them. These include veterans’ censuses, compiled service records, pension records, rosters, cemetery records, Internet databases, published books, etc.
- Kenneth E. Weant, Civil War Records:Missouri Enrolled Militia Infantry Regiments, Volume 8 (Arlington, Texas : K.E. Weant, c2010), pages #18-34. FHL book # 977.8 M2wka v. 8
- George W. Wanamaker, History of Harrison County, Missouri, (Topeka-Indianapolis [Indiana] : Historical Pub. Co., 1921), page 215-216. Internet Archive, (accessed 8 May 2013).