The Reserve Corps appear to be a 90 day regiment called up for the defense of the larger cities of Missouri - the 2nd regiment guarded bridges in St. Louis.
Information on R. T. Van Horn:
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Robert Thompson Van Horn (May 19, 1824 - January 3, 1916) was a lawyer, the owner and publisher of the The Kansas City Enterprise, mayor of Kansas City, Missouri during the parts of the Civil War, member of the Missouri General Assembly, and representative to the Forty-seventh Congress of the United States.
Born in East Mahoning Township, Indiana County, Pennsylvania to Henry and Elizabeth (Thompson) Vanhorn, he moved to Pomeroy, Ohio in 1844, studied law and was admitted to the bar about 1850.
He moved to Kansas City in 1855, was a member of the board of aldermen in 1857; postmaster of Kansas City 1857-1861 Van Horn purchased the newspaper The Enterprise in 1856 and renamed it The Kansas City Journal, which published daily from 1858 until its closing in 1942.
Van Horn was elected mayor of Kansas City to three terms, in 1861, 1863, and 1864.
He enlisted in the Union Army during the American Civil War and served as lieutenant colonel of the Twenty-fifth Regiment, Missouri Volunteer Infantry; member of the Missouri State Senate 1862-1864; elected as a Republican to the Thirty-ninth, Fortieth, and Forty-first Congresses (March 4, 1865-March 3, 1871); was not a candidate for renomination in 1870; chairman of the Republican State central committee 1874-1876; collector of internal revenue for the sixth district of Missouri 1875-1881.
He was a delegate to the Republican National Conventions in 1864, 1868, 1872, 1876, 1880, and 1884; member of the Republican National Committee in 1872 and 1884; elected as a Republican to the Forty-seventh Congress (March 4, 1881-March 3, 1883); successfully contested the election of John C. Tarsney to the Fifty-fourth Congress and served from February 27, 1896, to March 3, 1897; unsuccessful candidate for renomination in 1896; retired from editorship of The Kansas City Journal in 1897; died on his estate, “Honeywood,” at Evanston Station, near Kansas City, Missouri., January 3, 1916; interment in Mount Washington Cemetery, Kansas City, Missouri.
Van Horn High School was built on the site of Van Horn's Independence, Missouri house, Honeywood, in 1955. Truman Road was originally called Van Horn Road in his honor.
Text of the marker:
In June – July, 1861, barracks and service buildings within a 200-foot-square earthwork were built on this site by the battalion of United States Reserve Corps, Companies A, B, and C, organized by Major R. T. Van Horn, then Mayor of the City. By these means Kansas City was held to the Union throughout the Civil War while border fighting harassed the county. The cellars of the unfinished Coates Hotel on the west were used as cavalry barns.