Since what time did the majority of wars begin for the United States of America? In my generalized opinion, after the year 1913. And what occurred in 1913? The first 'illegal' President of The United States sat in the Constitutionally established seat of President of The United States of America. No Person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President; neither shall any Person be eligible to that Office who shall not have attained to the Age of thirty five Years, and been fourteen Years a Resident within the United States. The adoption of the constitition occurred in 178(7)-(9). Each prior President had lineage which was able to be traced back to their own lineage's citizenship back to 178(7)-(9). The first U.S president who could not/nor did meet this Constitutional requirement became President of The U.S.A in 1913.