Very cool place Don. This is what I found from an Army Corp Water Project Study document:
Moosa originally was Pamoosa, an Indian word probably meaning "long beard" in reference to a feathery waterfall at the head of the canyon. When the post office was designated, the United States Postal Service shortened the name to Moosa to avoid possible confusion with Pomona, California. The first settler in Moosa Canyon was Captain John Brown, who came there in the 1850's. The notorious California bandit Joaquin Murietta was also said to have a hideout in Moosa Canyon. In 1868 a settler named Kincaid was known for his stucco house covered with sticks in wickiup style. Later, Pat O'Neill started a store at Pamoosa, at that time the only store between Temecula and Bernardo. The writer Washington Irving and a man named Durand bought O'Neill out about 1870, and Irving became the first postmaster of the Moosa Canyon post office (Davidson 1934-1937:No. 91
An early pioneer of Moosa Canyon was W. D. Frazee, a preacher who had a strong interest in education and began one of the first schools in the area. In 1884 it was reported that W. D. Frazee had posted notice that religious services would be held in the Moosa
schoolhouse. It is thought that nearby Mt. Ararat received its biblical name from W.D. Frazee (Davidson 1939d). One of the best known landmarks of the Moosa Canyon district is Frazee's Castle, built by Isaac J.Frazee, son of W. D. Frazee, about 1893. Isaac found the rustic locale ideal for his pursuit of art and poetry, and he entertained many literary visitors in his castle. He was also the Moosa postmaster in the 1890's. at that time there were 21 families living in the canyon. Frazee's medieval style building was dubbed the "Castle" bN his neighbors and the name stuck. Frazee himself called it Warland Tower. and even though it is recorded as having been built in 1893, the Lummis report of 1902 notes that "the balance of the castle is not yet built." Frazee's Moosa Canyon property was one of the parcels considered by the Lummis Commission as a new home for the Cupeno from Warner's Hot Springs. At that time, Frazee, in his proffer, stated that the tower "would make an ideal home for the chief" (Freeman 1963. Lummis 1902: 172).
Moosa Canyon was the site of the celebrated Goings tragedy in 1888. In 1887 Levi Stone left his homestead to sell honey from his apiary. established as part of his land claim 10 years before. He returned to find squatters, the Goings family. in his house. Stone went
to the justice of the peace at Bear Valley for a writ of ejectment. then enlisted the aid ot Constable "Doc" Breedlove and Deputy Constable Arch Freeman to serve the writ. Stone hired Stockman Reed to drive his wagon, Freeman deputized George Morris to assist. and Stone's brother James M. Stone also went along. On January 18, 1888, they served the writ. but the Goings refused to leave. Peg Leg McConahay. one of the sons of old Mrs. Goings. shot Stockman Reed. and in the ensuing battle Percy Goings, Peg Leg, and Mrs. Burnham (a married daughter of Mrs. Goings) were killed. A jury charged Peg Leg with Reed's death. and held that the others died from shots inflicted by parties unknown, due to the confusion of the battle. Because of the public outcry in San Diego. especially over the death of a woman, Mrs. Burnham, the entire posse was charged with murder. All charges were dismissed except those against Freeman, who was acquitted, but a civil suit was filed by the Goings family and a judgement of $60,000 was awarded to Mrs. Burnham's husband, James. The judgement was never paid, rightfully so according to Moosa Canyon people who were angered at the unfairness of the judgement rendered by the city folk in San Diego. The foundations of the Levi Stone house were still visible in 1935 (Wright 1935).