In 1748, Frederick County was formed by carving a section off of Prince George's County. Frederick Town (now Frederick) was made the county seat of Frederick County. The county originally extended to the Appalachian mountains (areas further west being disputed between the colonies of Virginia and Pennsylvania until 1789). The current town's first house was built by a young German Reformed schoolmaster from the Rhineland Palatinate named Johann Thomas Schley (died 1790), who led a party of immigrants (including his wife, Maria Von Winz) to the Maryland colony. The Palatinate settlers bought land from Dulany on the banks of Carroll Creek, and Schley's house stood at the northwest corner of Middle Alley and East Patrick Street into the 20th century. Schley's settlers also founded a German Reformed Church (today known as Evangelical Reformed Church, and part of the UCC). Probably the oldest house still standing in Frederick today is Schifferstadt, built in 1756 by German settler Joseph Brunner and now the Schifferstadt Architectural Museum.