Establishing the US-Mexican border was accomplished in two stages. The first stage was helping the Mexicans achieve their independence from Spain in 1821 by having American and English troops give them a helping hand, and that had turned out marvellously well. The Mexican-American War of 1846 was the second stage. That’s when Lionel, head of the banking dynasty in the City, decided to promote the idea among members of the US Congress that it was advantageous for America to have a permanent southern border. Lionel had devised a very simple plan. Congress would send US troops to occupy Mexico City in order to force Mexico to relinquish its claims with regards to Texas and other parts of the American south. He would offer generous compensation to the Mexican Government, but the American troops would remain in Mexico City until the Mexicans signed the Treaty of Guadalupe Hidalgo.
When General Winfield Scott entered Mexico and won the Battle of Mexico City, it marked the unofficial end of the Mexican-American War of 1846. The Treaty of Guadalupe Hidalgo was signed and it stipulated that Mexico recognized the U.S. annexation of Texas. Mexico was also agreeing to the sale of California, as well as all of its territory north of the Rio Grande. The U.S. was to pay $15 million for the territory to be annexed, and $3.25 million to settle claims of American citizens against Mexico. It gave the United States the Rio Grande as a southern boundary along with the ownership of California and a large area comprising roughly half of New Mexico, most of Arizona, Nevada, and Utah, and parts of Wyoming and Colorado. Mexicans in those annexed areas were expatriated to Mexico unless they declared loyalty to the US government. Over 90% chose to pledge loyalty in exchange for not losing their homes.
The northern border keeping the French Catholics, the English Loyalists, and the many disgruntled natives north of the 49th parallel, was defined by the Oregon Treaty in that same year. Having drawn a straight line along the 49th parallel, and another along the Rio Grande extending to the Pacific Ocean, the Manifest Destiny concept had become a reality. America was now a predominantly white, English-speaking and Protestant country from coast to coast, with Canada to the north and Mexico to the South. The Spanish-speaking population remaining in the US would be overwhelmed, and the recalcitrant natives would continue to be forcefully relocated on Indian reserves.
In America, the first locomotive had been manufactured as early as 1830, but transportation remained limited to steam boats navigating canals and the Mississippi River and to short rail systems east of the Mississippi. The Oregon Trail was a primitive way to go west to the Pacific coast, but that didn’t include California. So, now that the Spanish-Mexicans were no longer a threat, Lionel in the City launched his plan to populate California with ‘white Americans’. He had been waiting for this moment to start a gold rush. He knew there was gold in California, of course, and since the telegraph had been clicking away throughout America and Europe since 1844, it was just a matter of letting everybody know there was a lot of gold waiting to be picked up off the ground. Some 300 000 individuals moved in, easily displacing, when not massacring, the native populations, and overwhelming the Spanish speaking population. California went straight into statehood. As a bonus, close to 4000 tons of gold was produced, bought up, and stockpiled, making both the City bankers and the miners very happy