Roads & Bridges » Las Vegas and Phoenix are the only two cities with populations more than 1 million that are currently not connected by an interstate. The I-11 looks to change all that. The first phase in Boulder City is expected to be complete by the fall of 2018. Phase 1 will construct about 15 miles of new freeway around the southern and eastern perimeter of Boulder City, Nev., from I-515 to U.S. 93.