Who was still permitted to enter the United States after April 6 1917? Was there still some immigration?
That was the date the US declared war on Germany, for those who don’t have it tattooed on their forearms.
Immigration to the United States slowed to a trickle because of the war, down to a low of 110,618 people in 1918, from an average of nearly 1 million. Those immigrants who did arrive in the United States faced difficulties beyond just the risks of travel. Some people found themselves stuck in a kind of limbo when they failed to pass inspection upon arriving in the United States, but were unable to be sent back to their homelands because of the war. So many found themselves in this situation that immigration officials had to develop parole procedures so that such individuals would not have to be detained in federal facilities for the duration of the war.
Immigration had already been slowed by the Immigration Act of 1917, which added a literacy test, narrowing the number even of Europeans who could enter
My father (as a child) and his parents came in after WWI, in the 1920’s; but had to come in from Canada, because the USA wasn’t accepting Jews coming directly from Europe.
There have been some people coming in legally all along. But at least since the Chinese exclusion laws in the 1800’s it’s been a lot easier for members of some groups than for others; and it seems to have been becoming harder since, though the specific restrictions vary from time to time – restrictions based openly on religion have gone out of style, but restrictions based on country of origin in effect still exist, as each country has a quota. AIUI some of the issue right now is that the backlog for most people is so large, and moving so slowly, that even those who theoretically are supposed to be allowed in can’t in practice get legally admitted.
Isaac Asimov and his family immigrated directly from Europe to the US in 1923, under what is now sometimes called chain migration (his mother’s half-brother had already immigrated some years earlier, and he sponsored Asimov’s parents, Asimov himself and his little sister (his little brother was born in the US)). Asimov noted that the 1924 Immigration Act would have kept his family out