Originally posted by storch
if you consider that the southern part of the US and all of california was discovered and largely settled by the spanish then your premis is off.
The treaty ceding California, Arizona, Utah and Nevada and parts of Colorado, New Mexico, and Wyoming was signed in Feb, 1848.
In January 1848 California's non-Indian population numbered about 14,000.
By the end of 1849, it had risen to nearly 100,000, and it continued to swell to some 250,000 by 1852.
14,000 Mexicans settled in all of California.