When is the earliest time in history when a woman could have run for President in the United States?

Women in the U.S.A. were first recognized as having the right to vote in 1920.

Iceland has had female presidents at least since 1980 and Vigdís Finnbogadóttir was the first female president ever elected in the world. British Prime Minister Margaret Thatcher, a conservative, served a similar role beginning as early as 1979.

Churches in the U.S.A. especially those associated with the Holiness movement, have had high ranking female leaders in traditionally male roles since the very early 1800s, in the Second Great Awakening. All in all, the idea of female leaders has been embraced even by conservatives for many years.

Hillary Clinton was the first female candidate for president.

Yet we still have never had a female president.

So, what is the EARLIEST a woman could have run for president in the United States?