The Sixteenth that I am referring to is the 16th Amendment to the Constitution which is the amendment that created the Income Tax. Ratification by the requisite number of states was completed on February 3, 1913 when Delaware became the 36th state to ratify. Thereafter, another six joined including New Mexico and Wyoming which also ratified on February 3rd. Several states rejected it or never considered it. Of course, after ratification it had to be implemented and explained.
A number of years ago – after receiving several questions that were related to the income tax I created a short guide with some sources for those who wanted to know more about the history. The data gathered by the IRS from the forms is something that I find particularly useful for business research, and in 2011 I wrote a post about some of the data collected by the IRS. Since that post they have added a bit more – particularly to their Archive – which makes me happy.