Legal Tender Note Series

Does anybody know why Legal Tender Notes were issued in Series 1862, 1869, 1874,1875, 1878, etc?  Why were so many needed so frequently?  Has any research been done?  I have wondered about this for a while. Any assitance is greatly appreciated.

Christopher Baker's picture

Mainly needed to pay national debts, most popularly and initially, "They were originally issued directly into circulation by the U.S. Treasury to pay expenses incurred by the Union during the American Civil War. Over the next century, the legislation governing these notes was modified many times and numerous versions were issued by the Treasury."

Basic information about the Legal Tender Acts can be found at this Wikipedia link.