Tree-ring analyses of baldcypress (Taxodium distichum) from Reelfoot Lake, Tennessee, support historical accounts that the lake formed during the great New Madrid earthquakes of 1811–1812. Due to ground subsidence and permanent flooding all of the bottomland hardwood trees within the impounded area were killed. However, many water tolerant baldcypress survived, and hundreds of 200 to 800 year old baldcypress outline the positions of former stream channels drowned by the subsidence. Dendrochronological analyses of multiple cores from 21 baldcypress in the lake reveal several pronounced growth responses to the 1811–1812 earthquakes. These responses include a great surge in radial growth during the decade following the earthquakes and a permanent reduction in wood density beginning in 1812. These and other growth responses to the 1811–1812 earthquakes may allow detection and dating of other large earthquakes in the Reelfoot basin during the late Holocene and may help date the formation of other suspected sunk lands in the New Madrid seismic zone.