Under the Charter of 1876, Overstolz was also the first St. Louis mayor elected for a four-year term. During his term, he guided the new government in its new relationship with the County and State. Ordinances were passed re-defining the powers and functions of various government departments. The office of commissioner of supplies was set up to do the purchasing for all institutions of the City government. The City assumed the bonded debt of the County.

Mayor Overstolz was born in Munster, Germany and came to St. Louis in 1846 to engage in the merchandising business. He married Miss Philippine Espenschied, the daughter of a prominent St. Louis citizen. He was elected to membership in the City Council in 1847. In 1853 he became comptroller. He was the first native-born German to be elected to city office in St. Louis. He was elected to the presidency of the council in 187l.

In 1875 he ran for mayor on an independent non-partisan ticket, but was declared the election loser by the election officials. Nine months later, the council seated him as mayor after a re-count of the ballots. In 1877 he was nominated for re-election by both the Democratic and Republican conventions.

During the later years of his life, Mayor Overstolz was engaged in banking and insurance interests. He died November 29, 1887. Burial was at Bellefontaine Cemetery.