I drove the I-40 route from DC to CA after 9/11...I never passed through St. Louis.
We have our little branch of it here. We have four interstates that merge at that bridge (I-70, I-40, I-44, and I-55)I think 40 disappears in Illinois and becomes I-64 heading to Kentucky or Tennesee. Out here in St. Louis county though the road is highway 40 or I-40.