Joshua Tree National Park is a US National Park located in southeastern California, straddling north-central Riverside County and part of southern San Bernardino County. Named after the endemic Joshua tree, found in the park and surrounding areas, Joshua Tree is situated some 130 miles east of the city of Los Angeles and roughly 78 mi east of the city of S…Joshua Tree National Park is a US National Park located in southeastern California, straddling north-central Riverside County and part of southern San Bernardino County. Named after the endemic Joshua tree, found in the park and surrounding areas, Joshua Tree is situated some 130 miles east of the city of Los Angeles and roughly 78 mi east of the city of San Bernardino. Among some of the closest cities to the park are Indio, Palm Desert, and Palm Springs. Originally declared a national monument in 1936, Joshua Tree was redesignated as a national park in 1994 when the U.S. Congress passed the California Desert Protection Act.