American history is full of little surprises like this. Looking for information on an unrelated topic, I stumbled across this little nugget:
"The period from about 1840 through about 1910 was оnе in which а considerable number оf states permitted aliens (those who had filed first papers, as а rule) to vote in elections."
The states in question, and the date when they ended this practice:
Arkansas -- until 1925
Colorado -- until 1902
Illinois -- until 1870
Indiana -- until 1921
Iowa -- until 1857
Michigan -- until 1924
Minnesota -- until 1896
Nebraska -- until 1910
North Dakota -- until 1898-1902
Ohio -- until 1851
Oregon -- until 1914
South Dakota -- until 1918
Wisconsin -- until 1908
This seems to be a midwestern and western phenomenon. Only one southern state (Arkansas), no northeastern states.
One consequence of this: "[T]he 1928 election was the first presidential election in which American citizenship was а universal prerequisite for voting."
This information comes from the Historical Statistics of the United States, Volume II, p. 749.