The crater's location is midway between Barstow and Needles and is about from either of these small cities. Amboy Crater is accessible to tourists via Interstate 40 as well as National Trails Highway - Route 66.
This cinder cone type crater is estimated to be around 6,000 years old and was formed in layers of mostly vesicular pahoehoe - possibly in the Holocene geological period. Lava flows as old as Amboy Crater itself blanket the immediate area. The crater is above sea level, about above the surrounding lava fields, and there is a false trail which is not advised for use in reaching the volcano's rim. The Federal Bureau of Land Management (BLM) recommends using the west trail found at the day use parking area. This unmarked, steep, and rocky hiking trail leads to the top of the cone which made Amboy Crater a popular U.S. Route 66 tourist stop before the opening of I-40 in the mid 1960s. Other than a stretch of US 66 through New Mexico, Amboy Crater was the only extinct volcanic area along the entire route and generations of Route 66 travelers from the 1920s through the 1960s could honestly boast that they had climbed a real volcano.
Amboy Crater and Lava Field were designated a National Natural Landmark in May, 1973. Visits from tourists have increased in recent years after having been forgotten upon the opening of Interstate 40 through the area.
Regular desert precautions apply: watch for snakes and other desert wildlife, bring abundant drinking water, hat, sunscreen, and sturdy shoes. It is best to avoid visiting Amboy Crater in summer conditions or in windy weather. Educational and organizational groups are advised to contact the BLM before heading out to Amboy Crater (to ensure adequate parking availability). BLM's Needles Field Office telephone number is +1 760 326 7000. Shaded and unshaded picnic tables are available, as are public restrooms.
Edit Addendum: According to the BLM sign at the site, the last eruption could have been as recently as 500 years ago.