The rural sections of the freeway were completed later than those in the urban areas. Construction of the highway in Corpus Christi and Nueces County continued north over the Nueces River into San Patrico County. The interchange at US 77 (future I-69E) was completed in 1969. The road that was already in existence along this stretch, SH 9, would be utilized as a frontage road as many of the bridges along this stretch were from when SH 9 was built in the 1930s. The main lanes were extended northward to SH 234 in 1969. By 1970, the freeway had been extended as far north as SH 188. In 1971, I-37 reached FM 888 and service to the city of Mathis. During the mid-1970s, the southern section and northern section were both being extended. The southern section was extended northward in Live Oak County to US 59 (future I-69W) in 1975 and FM 799 in 1976. The northern section saw completion in Atascosa County to FM 541 in 1975 and FM 1099 in 1976. By the early 1980s, the freeway was nearly complete. In 1980, the interchange at US 281 southeast of Pleasanton was complete. With the completion of the interchange at SH 72 and other bridges in the Pleasanton area in 1981, I-37 was complete.