The largest NMSZ earthquake of the 20th century was a 5.4-magnitude quake ( although it was reported as a 5.5 at the time ) on November 9 , 1968 , near Dale , Illinois . The quake damaged the civic building at Henderson , Kentucky and was felt in 23 states . People in Boston said their buildings swayed . At the time of the quake , it was the biggest recorded quake with an epicenter in Illinois in that state 's recorded history . In 2008 in the nearby Wabash Valley Seismic Zone , a similar magnitude 5.4 earthquake occurred with its epicenter in Illinois near West Salem and Mount Carmel
a 5.4-magnitude quake
1968 Illinois earthquake
New Madrid Seismic Zone