How can I find Highway 91 today?

Today, Highway 91 is found by traveling Interstate 15. I-15 follows the general direction taken by Highway 91, with some streamlining. Today's path speeds through California, Arizona, Utah, Idaho and Montana. In Southern California, I-15 is seen on maps coming from Arizona south to Riverside where it turns further south and the 91 Freeway continues west into Los Angeles. The plan was for Highway 91 to continue west to the Pacific Ocean. It doesn't quite make it to the ocean, but terminates only a few miles from there in the City of Hawthorne.