In 1875 Henry Overstolz became the twenty-eighth Mayor of St. Louis.
He was the first Mayor under the Charter and Scheme of 1876. This Charter and Scheme provided for the separation of St. Louis City and County. The Missouri Constitution, adopted in 1875, made possible the separation of the City and County. The Board of Freeholders, provided for in the Constitution, drew up the plan (called Scheme) of separation and the new City Charter. The Scheme of separation was ratified by vote of the people of the whole County, including the City. The City Charter was approved by the City's population as extended by the new city limits, which were moved westward from Grand to Skinker Avenues. The City was divided into 28 wards. The legislative power of the City was vested in a two-house Municipal Assembly, the Council and House of Delegates. The Charter of 1876 provided for a four-year term for the Mayor.
Mr. Overstolz was the first St. Louis Mayor elected for a four-year term. During this four year period, he guided the new government in its new relationship with the County and State. Ordinances were passed re-defining the powers and functions of the old departments, and those new ones transferred to the City under the Scheme of Separation. The office of Commissioner of Supplies was set up to do the purchasing for all institutions of the City Government. The City assumed the bound debt of the County. The City's area was increased from 20 to 61 square miles.