Last night my family made an all-night road trip from Provo to San Diego. The moon was new and the sky was clear for the first time in recent memory. During my turns in the passenger seat, I saw Orion, Canis Major, the Milky Way in Cassiopeia, and I'm fairly certain I even saw the evening zodiacal light in the dark area between Nephi and Fillmore.
I took this photo at the rest area between Baker and Barstow, CA. I took a moment to seek cover from the streetlights and was rewarded with a spectacular view of a star-studded sky. But I could definitely see the glow of Las Vegas on the northeastern horizon, and the Los Angeles metro area on the south.
I wonder if there is any area in the continental US (with clear horizons) where no artificial light is visible at night?