Phantom Ranch is a real location within the Grand Canyon on the north side of the Colorado River near its confluence with Bright Angel Creek and Phantom Creek. It's at Mile 88.1 (if you are using the Canyon standard measurement of Lee's Ferry as being Mile Zero).
The site where the ranch is now located was used by Native Americans; pit houses and a ceremonial kiva dating from about 1050 have been found there. John Wesley Powell and his exploration group camped at its beach in 1869. The Grand Canyon and Phantom Ranch was incorporated into the National Park System in 1919.
The site now includes cabins, two dormitories each for men and women, a restaurant (serving only people who book meals ahead of time), a mule corral, emergency medical facilities, a ranger station, the Bright Angel Campground, a beach that is frequently visited by Colorado River rafters, and a heliport. Cottonwood trees line the creeks and shade the buildings.
The only modes of access to the Ranch are foot trails (also used by the mules - don't step in a mule pie) and the Colorado River. Phantom Ranch also holds the distinction of being one of the only two places left in America whose regular U. S. Mail service is still delivered by pack train.
Most of the above was derived from the wikipedia page at http://en.wikipedia.org/wiki/Phantom_Ranch
There is a daily mule train that goes down and back up Bright Angel Trail to carry Ranch supplies in, the trash out, and the mail both ways. Mule rides are available, but reservations are necessary, at least six to eight months in advance, and the mule reservation includes an overnight cabin stay at the ranch. There is a 200 pound (91 kg) weight limit for each person and they DO weigh everyone (remember to pack very light... even if you don't have to carry the weight, the mules do!) It's NOT cheap... as of early 2012 the prices were close to $500 for one, $850 for two.
The Bright Angel Trail is a popular hiking trail, but the mules have the right of way, and it's not for the amateurs - over 5000 feet of ascent in about seven miles (over 1.5 km of ascent in in about 11.2 km) of distance makes for a steep trail.
In the Spearfish Lake Tales Universe you find Phantom Ranch as being a mail stop, telephone, general store (the Park Service calls it the Canteen), heliport (for medical evacuations) and crew change point (the new crew hikes down Bright Angel Trail from Grand Canyon Village, and the replaced crew hikes back up it).