I decided to keep this contribution from Jim Templeton at full size, so you can get the full effect of this sign goof. Jim took before-and-after pictures (below) of a sign goof that MoDOT fixed within a few weeks. As Jim describes it, "Shortly after the new overpass of McDonnell Blvd over I-270 opened in North St. Louis county, a co-worker of mine pointed out that no matter which direction you went on I-270, you would end up in Chicago. A few weeks later, the mistake was corrected."
Photos courtesy of Jim Templeton (taken 2004 as shown on the photographs).