Over the past 40 years SH 73 has been subjected to several route changes both in the Christchurch and the Arthur's Pass-Otira areas. In the early years SH 73 originally ended at the Blenheim Road and Hansons Lane corner in Upper Riccarton. In 1999, one of the worst sections of highway in the country (around Candy's Bend) were replaced with the Otira Viaduct. Meanwhile, in Christchurch, since SH 1 was rerouted to bypass the CBD, SH 73 was extended to Brougham Street/Waltham Road intersection, with the rest of the route covered by SH 74.