20 C.F.R. § 416.1615
(a) What you should give us. You can prove that you are lawfully admitted for permanent residence in the United States by giving us—
(b) What to do if you cannot give us the information listed in paragraph (a). If you cannot give us any of the documents listed in paragraph (a), we may find you to be lawfully admitted for permanent residence in the United States if you—
(c) What “United States” means. We use the term United States in this section to mean the 50 States, the District of Columbia, and the Northern Mariana Islands.
(Approved by the Office of Management and Budget under control number 0960-0451)
[47 FR 3106, Jan. 22, 1982, as amended at 52 FR 21943, June 10, 1987; 56 FR 55075, Oct. 24, 1991; 61 FR 56134, Oct. 31, 1996]