Within Mammoth Lakes, State Route 203 is known as both "Minaret Road" and "Main Street."

West of SR 203's western terminus, the road continues locally as "Postpile Road" or "Minaret Summit Rd" for 8.5 miles passing Devils Postpile National Monument and ending at Red's Meadow Resort and Pack Station.

East of US-395, the road continues for 1.7 miles as "Old Hwy" connecting utility yards and rural residences to the route.

[2] The highway usually closes between Minaret Summit and the Main Lodge of Mammoth Mountain Ski Area before Thanksgiving and usually does not open much before Memorial Day.

[4] Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, based on the alignment that existed at the time, and do not necessarily reflect current mileage.