in 1636 took a heavy toll on the population. In 1664, Archbishop Johann Philipp of Mainz sold his brother Philipp Erwin of Schönborn the two villages for 9,000 Gulden. In 1806, the Schönborn Amt of Heusenstamm with Hausen and Obertshausen was mediatized into the Principality of Isenburg, which was in turn mediatised ten years later. Both places then passed with the Isenburg Amt of Offenbach to the Grand Duchy of Hesse, and as of 1945, to the state of Hesse. From the Middle Ages until 1819, Obertshausen and Hausen belonged to the Biebermark, an area held in common with several other villages. In 1819, the Biebermark was divided among the member villages. In 1896, the Offenbach-Dieburg railway opened with a railway station in Obertshausen. In the course of municipal reform in Hesse, the two formerly self-administering communities of Obertshausen and Hausen were merged. At first, the new community was named Hausen. On 1 January 1978, however, it was named Obertshausen. The two centres are separated from each other by Bundesstraße 448. On 29 September 1979, the Hesse state government granted Obertshausen town rights. Population development In 1576 there were 10 households in Hausen and 27 in Obertshausen. In 1834, Hausen's population had risen to 444 and Obertshausen's to 554. These figures have risen to many times these old levels over the years since then. By 1939, the figures had become 2,034 and 2,444 respectively. On 30 June 2007, the town as a whole had 25,314 inhabitants, of whom 12,668 lived in Hausen and 12,646 in Obertshausen. Inhabitants (each time as at 31 December) 1998 – 24,522 1999 – 24,577 2000 – 24,658 2001 – 24,676 2002 – 24,521 2003 – 24,484 2004 – 24,532 2005 – 25,434 2006 – 24,210 Politics Town council The municipal election held on 26 March 2006 yielded the following results: Mayor Mayoral elections take place in Obertshausen every six years. The most recent mayors were: 2002–2014: Bernd Roth (CDU) 2014–2020: Roger Winter (independent) 2020–incumbent: Manuel Friedrich (independent) Coat of arms The town’s arms might be described thus: Party per fess abased dancetty of three, gules a lion passant crowned Or, his paws on the peaks of the parting, argent in base an oak sprig with two leaves and one acorn vert. Flag The town's flag has a white field in the middle flanked by a red stripe at each side, and in the upper half