In my father's family tree, when Vilna-born merchant Samuel Markell (1885-1971) married Boston-born Marion Goldstein (1885-1961) in Revere, Massachusetts in 1911, the new bride took her husband's surname--and also his nationality. He was "Russian" and she became "Russian" at the moment of their wedding.
This was due to the US law known as the Expatriation Act of 1907, which tied a woman's citizenship to that of her husband. By marrying an alien, Marion Goldstein Markell was transformed into a marital expatriate for three decades. Samuel became a US citizen in 1923 but that didn't change his wife's status.
Changes under the Cable Act
After World War I, and an outcry from US women who gained the right to vote starting in 1920, Congress passed the Cable Act of 1922 to restore citizenship eligibility to women who were marital expatriates. However, the women had to actually apply for naturalization as though they had not been American-born. Many did not. By 1936, US law streamlined the process of allowing marital expatriates to become US citizens.
Changes on July 2, 1940
Finally, on this day in 1940, a new law amended the 1936 rules. Now women who were marital expatriates could more easily "repatriate" and regain their citizenship, no matter their marital status. They still had to take an oath of allegiance.
And that's why, in June of 1941, Marion Goldstein Markell filed the paperwork to regain her US citizenship. In September of that year, she took the oath of allegiance. Thirty years after losing her US citizenship, she was again legally an American citizen.