Sections of the Bay Trail exist in all nine Bay Area counties. The longest continuous segments include 26 miles (41 km) primarily on gravel levees between East Palo Alto and San Jose in Santa Clara County; 25 miles (40 km) in San Mateo County between Millbrae and San Carlos; 17 miles (27 km) in central Alameda County from San Leandro to Hayward; and 15 miles (24 km) along the shoreline and on city streets through Richmond in Contra Costa County. The northernmost trail section passes through San Pablo Bay National Wildlife Refuge.