More than 300,000 new "alien files" have been released by NARA and are located at the Kansas City regional facility.The National Archives states, "A-Files
are a rich source of biographical information in that they
contain relatively modern immigration documents, all in one file. Since
the early 20th century the United States collected increasing amounts
of information from immigrants and A-Files from mid-century hold a
wealth of data, including visas, photographs, applications, affidavits,
correspondence, and more."
More info on searching the files and making requests here.