Interstate 635 (I-635) is a 37-mile-long (60 km) partial loop around Dallas, Texas, in the United States between I-20 in Balch Springs and State Highway 121 (SH 121) at the north entrance of the Dallas-Fort Worth International Airport in Grapevine. It intersects I-35E at exits 27B–C, but does not connect with I-35W. It is known locally as the Lyndon B. Johnson Freeway, or LBJ, named after Lyndon B. Johnson, the former U.S.