30 U.S. Code § 25 - Affidavit of citizenship

Applicants for mineral patents, if residing beyond the limits of the district wherein the claim is situated, may make any oath or affidavit required for proof of citizenship before the clerk of any court of record or before any notary public of any State or Territory.

(Apr. 26, 1882, ch. 106, § 2, 22 Stat. 49.)