All FAQs
This question was inspired by Alejandro, who asked specifically about the history of racism in immigration law and about quotas
As for racial issues in immigration: that's a tricky subject. Immigration law technically is racially neutral today, although in practice it is very heavily tinged by racism.
Going back in history, immigration has almost always been a racial issue. Actually, I shouldn't say "racial" but rather "anti-newcomer". The backlash rarely targeted a specific race as much as whatever group happens to be the main immigrating group at the time. Today, it is Hispanics, and is in the process of shifting towards Asian Indians. When I went to high school in Seattle in the 1980s, there was a very heavy anti-Vietnamese sentiment. Today, of course the Vietnamese are very well accepted. Before that, the targeted groups were the Puerto Ricans (just watch West Side Story, which very much reflects that!), Italians, Polish immigrants, Chinese, an earlier wave of Mexicans, ...
All these were public sentiments rather than legal issues of course.
In the legal arena, we used to have a few different approaches. Originally, until the early 19th century, you could just get off the ship and stay - but only Europeans would ever do that, so racism wasn't an issue yet. The first really restrictive immigration law was the Chinese Exclusion Act from the 1880s or so. That law basically still allowed unlimited immigration, but not if you were of the "Asian Race". Interestingly, it's background is exceedingly similar to today's backlash against Mexicans: many of the railroad workers in California decided to stay. That is why all the major railroad cities on the West Coast have Chinatowns (San Francisco and Los Angeles are best known). Caucasian Californians did not like the competition.
So this law was explicitly racist. It also ended up more or less unsustainable, and was replaced in 1924 by the "national origin quota" that you already mentioned. That, too, was designed to be racist, but it only gave a preference to Europeans, rather than outright banning other nations. I didn't remember the detail about "percentage of people already in the USA" but since you mentioned it, you are right - that's how it worked. And due to the Chinese Exclusion Act, it effectively perpetuated the exclusion of Asians. Please note that this is very fundamentally different from the quota system we use today!
At the same time, it was also the first time the USA capped the number of immigrants - until the 1920s, you could still come to the USA and be admitted just for the asking. At least if you were European and healthy.
All of that was basically done as ad-hoc laws. Immigration laws were all over the law books. After WW II, between the experiences with the Japanese Internment camps, the rejected Jewish refugees, and the events in Germany and Europe, there was a sentiment to abolish racism. For the first time, Congress wrote one comprehensive immigration law - the Immigration and Nationality Act, or INA. This is basically the immigration law we are still using today, although there have been changes.
The INA does have quotas. It actually has two separate quotas: one per category, and one per country. Initially, the quotas didn't really matter much because the quotas were much higher than the number of applicants. But over time, the quotas have been changed multiple times, and the number of people applying for Green Cards has increased dramatically, and today the quotas are stifling.
My Web page actually describes in more detail how the quota system works, but the general idea for the per-country quota is that no country should be able to send more than 7% of the worldwide number of immigrants (a little over 25,000 per country). I believe the intent was to prevent waves of immigrants from just one country the way we had in the past. But it didn't quite work out that way. It turns out that this per-country quota discriminates against large countries or countries with close ties to the USA. For instance, under the per-country quota, pretty much the whole population of Liechtenstein could immigrate in a few years. But India or China with a billion people each also only get the same 25,000 slots.
In fact, most countries in the world send fewer than 25,000 immigrants per year - those are called the "worldwide quota". India, China, Mexico and the Philippines are the only countries who reach their per-country quota. India and China are hardly surprising - they are simply big countries with booming economies, so there is a lot of demand for immigration. Mexico is also a pretty big country (100 million people) close to the USA, with lots of cross-border family ties. In addition, the 1986 amnesty allowed many Mexicans to become permanent residents, and eventually citizens, and now sponsor in turn their family members. That is why Mexico is on the list.
Of the four countries on this list, the Philippines is probably the most surprising one. And in fact, it has more applicants than India or China! The reason lies in its history. Until 1946, the Philippines were essentially a US colony, similar to Puerto Rico or Guam today. Filipinos were US nationals - not citizens, but had the right to settle in the USA. That means that there are very strong family ties between the Philippines and the USA. With the economy deteriorating and the Philippines also having political problems, crime and even Al-Qaeda terrorism, Filipinos want to emigrate to the USA and call on their family members. That is why the quota backlog for the Philippines is longest; in the Family 4th category, it is going on 25 years!
When I said above that immigration law is technically neutral, I am referring to the fact that it does treat each country equally. The adverse effect on India and China was probably not intended but a result of a poorly-thought-out system.
In practice, though, the level of scrutiny potential immigrants (and non-immigrants) face varies greatly from one country to the next. Some people argue that this is based primarily on the amount of immigration fraud from the affected countries, while others maintain that it there is racism involved.
