The visitor center in Devils Postpile National Monument is 16 miles from US 395 - 8 miles along Highway 203 through Mammoth Lakes as far as Main Lodge at Mammoth Mountain, then 8 miles in a shuttle bus along the Minaret Summit Road, across land of the Inyo National Forest. Early or late in the season, however, visitors may drive all the way in their own vehicle, as can all people camping or long distance hiking.

PDF format maps of Devils Postpile National Monument, from the National Park Service:
Park map (1.9 mb)
Area map (572 kb)