If you look at persons obtaining permanent resident status as a proportion of total population, it peaked in 1900-1910 and has been fairly stable since the 1990's: https://docs.google.com/spreadsheets/d/109xdKq3U7ISifgyjlQLL...

Sources:

https://en.wikipedia.org/wiki/Immigration_to_the_United_Stat...

https://en.wikipedia.org/wiki/Demographic_history_of_the_Uni...