Immigration requirements were much tighter in the 1950s for all groups, as there was not much desire for mass immigration for displaced persons from Europe after WWII.

At that time there were many fewer Mexicans living along the border, the factories did not exist and the center of population was much further south. Towns close to the border such as El Paso and San Diego had a much more relaxed policy, people could just walk across and it was not uncommon for people to live on one side and work on the other. Flying from Los Angeles to Mexico City was easy.

The flood of Mexican immigration to the U.S. did not start until the mid-1960s and it was not considered a matter of social or political concern until then.

In the 1950's, immigrants were allowed in based on the country from which they originated, and a certain amount of immigrants were allowed per country. However, immigration law has been through a few changes since then - immigration approval is now based on the family - so if you're allowed in as an immigrant, then your relatives are more quickly approved than an immigrant without family ties in the US.

The change in the law has increased the amount of immigrant flow into the US overwhelmingly, and coupled with illegal immigrants streaming over the border in record numbers, has increased the bill that taxpayers must fork over to support the increased population.