Interstate 238 is an Interstate Highway in the state of California in the United States. It goes from Interstate 580 in Castro Valley west to Interstate 880 in San Leandro. The route is long. The route is not like a 3-digit route as there is no Interstate 38. It is called Interstate 238 as it was a part of California State Route 238 and no numbers with "80" at the end were able to be used.