The Immigration Reform and Control Act was passed in 1986 under the Reagan administration. It legalized most illegal immigrants who had arrived in the country prior to January 1, 1984.

On signing the act into law at a ceremony held beside the newly-refurbished Statue of Liberty, Reagan said, "The legalization provisions in this act will go far to improve the lives of a class of individuals who now must hide in the shadows, without access to many of the benefits of a free and open society. Very soon many of these men and women will be able to step into the sunlight and, ultimately, if they choose, they may become Americans."

The act did not address the status of children of undocumented migrants who were eligible for the amnesty program, and In 1987, Reagan used his executive authority to legalize the status of minor children of parents granted amnesty under the immigration overhaul, announcing a blanket deferral of deportation for children under 18 who were living in a two-parent household with both parents legalizing or with a single parent who was legalizing. That action affected an estimated 100,000 families.

In his last speech as president, Reagan spoke on immigration:

You can live in Germany, Turkey, or Japan, but you can't become a German, a Turk, or a Japanese. But anyone, from any corner of the earth, can come live in America and become an American.
— Ronald Reagan, 1988

Wild to see the shift in rhetoric. This isn't just to the left of Republicans, its even to the left of Democrats.