In 1960, the U.S. census stopped asking about citizenship. This is why.

Questions 13 and 14 on the 1950 U.S. census asked, "What state (or foreign country) was he born in?" and "If foreign-born — is he naturalized?"
Market Update
SENSEX 31,622.48 -187.07(%)
NIFTY 9,898.00 -54.2(%)