The East Bay Regional Park District (EBRPD) is a special district operating in Alameda County and Contra Costa County, California, within the East Bay area of the San Francisco Bay Area. It maintains and operates a system of regional parks which is the largest urban regional park district in the United States. The administrative office is located in Oakland. As of 2015, EBRPD spans 120,000 acres (49,000 ha) with 65 parks and over 1,200 miles (1,900 km) of trails. Some of these parks are wilderness areas; others include a variety of visitor attractions, with opportunities for swimming, boating and camping. The trails are frequently used for non-motorized transportation such as biking, hiking, and horse riding. Nearly 150 miles (241 km) of paved trails through urban areas link the parks together. The EBRPD was founded in 1934, and acquired its first land two years later, when the East Bay Municipal Utility District sold 2,166 acres (877 ha) of its surplus land. The founders of the district included Robert Sibley, a hiking enthusiast, Hollis Thompson, then Berkeley City Manager, and Charles Lee Tilden, among others. William Penn Mott, Jr. served as director of the agency from 1962 to 1967, and oversaw a doubling of the systems acreage from 10,500 to 22,000.