In case anyone is curious, there have been a variety of different estate taxes at a federal level in the United States from 1797 through the present. https://www.irs.gov/pub/irs-soi/ninetyestate.pdf
The "modern" estate tax was enacted in 1916. It was repealed for a single year -- 2010 -- but returned the following year and is currently in force. The exclusion amount has grown considerably over time.