During the early years of the Interstate Highway System, branching Interstates with directional suffixes such as N, S, E, and W were common nationwide. On every other Interstate nationwide, these directional suffixes have been phased out by redesignating the suffixed route numbers with a loop or spur route number designation. In the case of I-35 in the Twin Cities area, since neither branch is clearly the main route and both branches return to a unified Interstate beyond the cities of Minneapolis and Saint Paul, officials at the American Association of State Highway and Transportation Officials (AASHTO) have allowed the suffixes of E and W in Minnesota to remain in the present day. I-35 also splits into I-35E and I-35W in Dallas-Fort Worth, Texas, for similar reasons as the I-35 split in the Minneapolis–Saint Paul area.