[6] The Branch family began homesteading the property, partially acquired from the Southern Pacific railroad, in 1880 or 1881.

[10][7] They were natives of Topeka, Kansas,[11] and William E. Gilman had previously owned a hotel in Ocean Park that had burned in 1912.

[16] The resort was said to have a "frame hotel and cottages and tents forming a little settlement in a grove adjacent to the springs.

[4] In 1917 a U.S. government geologist reported: "At the Relief group six thermal springs issue from a bank of disintegrated granite, and considerable water also rises in an adjacent marshy area several acres in extent.

The place has been a resort for more than 20 years, a frame hotel and cottages and tents forming a little settlement in a grove adjacent to the springs.

"[17] A fire in the winter 1917 "razed all the original buildings and demolished all the initial improvements the Gilmans had made".

[7] Many visitors arrived by train via San Jacinto, where they were met by representatives of the hotel to be transported to the resort.

[18] In 1930, visitors could get to Gilman's Hot Springs by either taking the Pacific Electric to Riverside and there connecting with a Motor Transit stage, or by taking a Santa Fe Railway train to San Jacinto, where an auto stage would then ferry them to the springs resort.

[26] Guests during the resort's heyday reportedly included Joe DiMaggio and Marilyn Monroe, Sugar Ray Robinson, and an unidentified president of Ireland.

[33] It is now a heavily guarded compound surrounded by high fences topped with razor wire and spikes, with a prison building nicknamed "The Hole", and is inaccessible to the public.

[34][35] The Church of Scientology demolished the Massacre Canyon Inn, the Gilman Garage, and the golf course to make way for new buildings.

[33] The hot springs are located on California State Route 79, 4 miles (6.4 km) north-northwest of San Jacinto.

Efflorescent alkaline salts collect along the banks beside the springs, and the iron and sulphide contents in the water stained towels and enameled tubs.