In 1818, in an effort to destroy Spain’s presence in California, Argentinean revolutionary privateer, Hipólito Bouchard attacked Monterey. After the only known land and sea battle fought on the West Coast, Bouchard sacked the town. The damage from Bouchards raid was quickly repaired and during the next decade, residents began to expand outside the Royal Presidio, building residences, creating streets, and inaugurating businesses that would establish the foot-print of modern Monterey.
In April 1822, the people of Monterey learned that Mexico had won its war for independence from Spain; California pledged allegiance to the Mexican Government. While Spain had discouraged foreigners to trade with California, Mexico opened the area to international trade. Monterey became California’s port of entry. British and American ships vying for the hide and tallow traffic became an important part of the economy. A dried steer hide valued at about a dollar was termed a "California Bank Note". The hides were shipped to New England, where they were used to make saddles, harnesses, shoes and other leather goods. Tallow was melted down in large rendering pots and poured into bladders, made of hides, and delivered to the waiting ships. The tallow was ultimately converted into candles or soap contributing to the commercial expansion of Monterey.
The Custom House was enlarged after 1827 to accommodate the expanding commercial activities in Monterey. Originally started in 1814, the Custom House is considered the oldest public building in California. The more open trade policy of Mexico made Monterey a cosmopolitan pueblo, including Americans who the Californios referred to as "Yanquis." Many of the newcomers married into Californio families, and became Mexican citizens. In response to the growing American presence in California the United States in 1842, established a consulate in Monterey. Thomas Larkin was appointed the first and only American Consul to California. His home, located at Pacific and Jefferson Street, is the origin for the architectural style renowned as "Monterey Colonial."
Under Mexican authority many land grants were made to private citizens and Monterey received its Pueblo grant of 30,000 acres. The once proud missions were secularized in the mid-1830s, and their lands were dispersed as part of the grants. In California those early settlers and native born citizens inherited the name of Californios. They became the romanticized vision of Mexican California that was reflected in such novels as Helen Hunt Jackson’s Ramona.
In July 1846, during the Mexican-American War, Commodore John Drake Sloat’s Pacific squadron arrived in Monterey Bay. On July 7, his troops landed, raised the American flag, claiming California for the United States. This began a period of American occupation that lasted until 1848 when the Treaty of Guadalupe Hidalgo was signed making all of Alta California part of the United States. This acquisition included the land now known as California, Utah, Nevada, parts of Arizona, Colorado, New Mexico, and Wyoming.
In Monterey, U.S. Navy Chaplain Walter Colton was appointed to serve as Monterey’s first American Alcalde, a position defined as Mayor and Judge, but which included many more duties. Colton, a graduate of Yale University and Andover Seminary, proved to be a just and honorable executive, well qualified to hold this important position. One of his many accomplishments was the design and supervision of the construction of Colton Hall, the first public building constructed under the American flag. Opened March 8, 1849, Colton Hall was originally built to serve as a public school and town meeting hall, but has proven to be much more.