Hospital Rock, an isolated lava formation on the south shore of Tule Lake, and the surrounding level land served twice as an encampment for United States troops attacking Captain Jack's Stronghold in the Modoc War of 1873. This was the only Indian War to be fought in California.

In 1872, after several years of disputes with settlers, Captain Jack and his band of Modoc Indians took refuge in the lava beds immediately south of Tule Lake.

On January 16, 1873, two troops of cavalry and twenty Indian scouts under the command of Capt. Reuben F. Bernard marched sixteen miles from Land's Ranch to a location near Hospital Rock. After being fired on by the Modocs, they retreated to Hospital Rock where they camped for the night.

The following day, Capt. Bernard's men attacked Captain Jack's Stronghold two miles to the west. When the attack failed, Capt. Bernard withdrew his men by way of Hospital Rock back to Land's Ranch.

In the following weeks, the US Army units moved ever closer to the Stronghold in preparation for another attack. On April 6, five companies commanded by Maj. Edwin C. Mason, 21st Infantry, camped at Hospital Rock.

On April 11, 1st Lt. William L. Sherwood and a fellow officer walked a half mile beyond the Hospital Rock fortifications carrying a truce flag. The Modocs attacked and killed them.

On April 12, the Modocs fired on pickets west of Hospital Rock, forcing some of them to withdraw.

On April 14, Mason advanced his men from Hospital Rock at night for the second attack on the stronghold. The US Army occupied the stronghold two days later.

The camp at Hospital Rock was broken up soon after the capture of the stronghold. Its important role as the base of operations for the eastern force during the attacks on the Modocs came to an end, although the war continued for another six weeks.

Source: NRHP Nomination Form submitted in August of 1973