 Much of Old 16 remains intact, however I-90 has absorbed sections and likewise has reshaped the economies of many southern South Dakota towns.On May 24, 2012, the South Dakota Transportation Commission declared the entire length of I-90 as part of the National Purple Heart Trail, naming it the Purple Heart Memorial Highway.In the city of Box Elder, exit 66, which crossed South Dakota Highway 435, was closed on October 1, 2003, after a 10-month delay.