In southern California, Marsh claimed he was the only person who had any knowledge of Western (or European-style) medicine. He presented his Harvard degree to the local Mexican government of
Alta California. The degree was written in Latin, which none of the local authorities could read. They took his word and granted him permission to practice medicine. Marsh was quite successful in his new profession, but his prices were very high. He sometimes charged as much as a head of cattle to deliver a baby. He is credited as being the first person to practice medicine in California. He was often paid in the currency of the day: cowhides and tallow. Marsh joked that his adobe looked more like a warehouse than the offices of a physician. In 1836, he sold his accumulated inventory to a Boston trader for $500 and rode to Northern California seeking a ranch to purchase. Since Mexico allowed only Catholics to own land in California, he became baptized as a Roman Catholic. In 1837, Marsh purchased the 17,000-acre
Rancho Los Méganos, a land grant, from prominent
Californio ranchero
José Noriega on what is now called
Marsh Creek. This was east of what is now
Clayton, California and on the western edge of the present-day city of
Brentwood. (His acquisition of the rancho indicates that Marsh had become a naturalized Mexican citizen). The price he paid for the rancho was $500 (all of his savings). He became the first known non-Hispanic white settler in what is now
Contra Costa County. Marsh prospered there, both as a rancher and as a doctor. He continued to invest by purchasing more land near his original rancho. Before his death, he claimed that his rancho contained about 40,000 acres of land. In practicing medicine, he again charged very high prices, generally in relation to how far he had to travel to see the patient (which often meant being away from his ranch for days or weeks). There is some evidence that during this period, he cared for some of the survivors of the
Donner Party. Marsh acquired tens of thousands of head of cattle for his rancho and lived the life of a wealthy
ranchero. He was known to pay very low wages to his workers, and many were said to hate him. In 1841, when the first American emigrant party, the
Bartleson-Bidwell Party, reached California from Missouri. There were 32 men and one woman and her baby. Marsh invited them to be his guests. The
California Trail thus terminated in Brentwood. After entertaining members of the Bartleson-Bidwell Party, Marsh was said to invite them to slaughter one of his steers for breakfast the next morning. The next day, however, he found that the party had also slaughtered his best work oxen, which comprised a highly valuable commodity and were critical to ranch operations. Although it was likely a mistake, Marsh was angry and bitter toward the party. Later there were further disagreements between them. John Bidwell reportedly said that "John Marsh is the meanest man I ever met." Among the Bartleson-Bidwell Party was
Nancy Kelsey, known as the first woman to cross the Sierras to reach California. She later became known as the "Betsy Ross of California" after she created the state's first flag. As early as 1837, Marsh worried about being able to retain ownership of the great rancho. Americans and some other foreigners considered the Mexican courts in California to be corrupt and unpredictable in their rulings on such cases. In addition, there was evidence of competition by the Russians, French and English, who were independently preparing to seize the province. Marsh was determined to have the territory become part of the United States to protect his holdings. He felt the best method to achieve that was to encourage emigration by Americans to California, and in this way repeat the history of Texas as a takeover by more numerous Americans. Marsh conducted a letter-writing campaign espousing the California climate, soil and other reasons to settle there, as well as the best route to follow, which became known as "Marsh's route." His letters were read, reread, passed around, and printed in newspapers throughout the country, and stimulated the first significant migration to California. Marsh invited immigrants to stay on his ranch until they could get settled, and assisted in their obtaining passports. During this period Marsh began a search to reunite with his son, Charles, but was unable to find him. In 1851, the Reverend William W. Smith introduced Marsh to Abigail "Abby" Smith Tuck, a schoolteacher from New England, who served as principal at a girls school in San Jose. After a brief two-week courtship, they married on June 24, 1851. Soon after the wedding, the couple moved into the old adobe. On 12 March 1852, she gave birth to a daughter they named Alice Frances. ==John Marsh House==