In December 1838, the General Assembly of Missouri passed an act providing for the organization of Platte and Buchanan Counties. James Buchanan, afterwards President, at that time represented the United States at the court of St. Petersburg. He was a popular idol at home, and this county was named in his honor.
The creative act authorized the governor to appoint a sheriff, to serve until the general election in 1840.
The early day Sheriff's of Buchanan County, in addition to their duties as peace officers, were also required to make collections of all sums due the county, including taxes. The first sheriff, Samuel Gilmore, was appointed by Governor Lilburn W. Boggs upon the formation of the County. Mr. Gilmore was re-elected in 1840 and held the office through 1842.