Linking to New Mexico in the south would prove more problematic as the planned route had to stretch over Raton Pass, and its accompanying elevation change, within just . Once again, US 85 and US 87 were used, but it had to be re-graded in places to meet Interstate design guidelines. Construction began in 1960, with a link to the city of Trinidad completed by 1963. The Trinidad Segment (as CDOT now calls the Raton Pass span) was not fully completed until 1968.