I-40 is an interesting case. It hits the ocean in Wilmington NC, but doesn't make it to the coast in California, ending in Barstow. The completionist in me says that it ought to continue through Palmdale to Ventura.

Until a few years ago, it wasn't contiguous. There was a gap in Memphis where the locals objected to its completion because the traffic noise would have disturbed the animals at the zoo. So the northern part of I-240 was signed to include I-40, finally linking the two halves together.