1909 — The 16th Amendment to the Constitution is sent to the states for ratification in 1909. It grants Congress the power to levy and collect an income tax.

Elsewhere that year:

• A. P. Davis is the self-professed founder of neuropathy.
• African-Americans and Caucasian-American leaders meet in New York and form the National Association for the Advancement of Colored People (NAACP) to fight for African-American rights.
• Three million acres of public lands in the West are set aside by President William Howard Taft for conservation purposes.
• The Lincoln penny, issued by the Philadelphia mint, replaces the Indian-head penny, which had been in use for 50 years.