1845: Henry David Thoreau took up residence at Walden Pond outside of Concord, Massachusetts. Thoreau's book about the experience has become a classic of American literature, urging people to look at nature to understand the universe.

Today: Most of what students know about the American philosophical movement known as "Transcendentalism" comes from reading Thoreau's Walden.

1845: Margaret Fuller published Women in the Nineteenth Century. A former editor of the Dial, Fuller urged women to be more independent: "That her hand may be given with dignity, she must be able to stand alone."

1920: After more than 50 years of struggle, women won the right to vote with the passage of the 19th amendment.

1982: The Equal Rights Amendment, which passed the Senate ten years earlier, failed to be ratified by enough states to make it law. The Amendment would have prevented the restriction of any citizen's rights on account...