Sister cities of Montgomery County, Pennsylvania

Montgomery County, locally also referred to as Montco, is a county located in the state of Pennsylvania in the United States. As of 2010, the population was 799,874, making it the third most populous county in Pennsylvania (after Philadelphia and Allegheny counties). The county seat is Norristown.

The county was created on September 10, 1784, out of land originally part of Philadelphia County. The first courthouse was housed in the Barley Sheaf Inn. It is believed to have been named either for Richard Montgomery, an American Revolutionary War general killed in 1775 while attempting to capture Quebec City, Canada, or for the Welsh county of Montgomeryshire (which was named after one of William the Conqueror's main counselors, Roger de Montgomerie), as it was part of the Welsh Tract, an area of Pennsylvania settled by Quakers from Wales. Early histories of the county indicate the origin of the county's name as uncertain.

Montgomery County is a suburban county northwest of Philadelphia. It is part of the Delaware Valley and marks the region's northern border, with the Lehigh Valley region of the state to the north. In 2010 it was the 51st wealthiest county in the country (measured by median household income). In 2008 it was named the 9th Best Place to Raise a Family by Forbes.