There is currently no Interstate Highway designated with the Interstate 9 (I-9) designation.
If I-9 was to be designated in the future, it will likely be designated somewhere along the U.S. West Coast, near Interstate 1, Interstate 5, Interstate 7, and Interstate 11.
Future[]
Interstate 7 or Interstate 9 has been proposed by Caltrans for State Route 99 in central California. It would go from the split with I-5 at Wheeler Ridge (Wheeler Ridge Interchange) north through Bakersfield and Fresno to Stockton, where the proposed route turns west via the State Route 4 freeway to a terminus at I-5 in the central part of that city. An alternate proposed terminus is located at the I-5/US 50/Capital City Freeway junction in Sacramento, where the future Interstate, after continuing north from Stockton along Route 99, can turn west along the Capital City Freeway, already an Interstate route (unsigned I-305), to connect with I-5, which extends north toward Redding. This also serves as a connector to the existing northern portion of Highway 99. The future Interstate's prospects for development to appropriate standards are tied to the Caltrans "Route 99 Corridor Enhancement Master Plan", which outlines improvements to that route, including capacity and physical improvements; this document posits that when and if Interstate status is conferred, the route will be designated either I-7 or I-9. In August 2005, with the passage of that year's SAFETEA-LU federal transportation legislation, SR 99 from Wheeler Ridge to Stockton and beyond to Sacramento was designated as High Priority Corridor 54, the California Farm-to-Market Corridor; this legislation also designated that corridor as a future segment of the Interstate System.