Railroad Pass
The I-515 designation was first approved by the American Association of State Highway and Transportation Officials (AASHTO) on July 12, 1976, from the I-15 interchange to the junction of US 93 and US 95 (at Boulder Highway, current exit 70). On December 7, 1984, AASHTO approved the southeasterly extension of the route to its former terminus near Boulder City. Even though the route number was approved prior to the highway's construction, I-515 was not consistently signed until after the freeway was completed down to its former southern terminus north of Railroad Pass in 1994.