Prior to I-37, the routing between Corpus Christi and San Antonio was covered by SH 9 from Corpus Christi to Three Rivers and US 281 from Three Rivers to San Antonio. Beginning in 1971, sections of SH 9 were officially removed from the State Highway System as I-37 was completed. No sections of US 281 were removed from the State Highway System as a result of the construction of I-37, but the two do share the same alignment at two different points between San Antonio and Three Rivers. Also, US 281 was rerouted onto I-37 in San Antonio in 1978.