1866 United States elections occurred in the middle of National Union/Democratic President Andrew Johnson 's term , during the Third Party System and Reconstruction . Johnson had become president on April 15 , 1865 , upon the death of his predecessor , Abraham Lincoln . Members of the 40th United States Congress were chosen in this election . As this was the first election after the Civil War , many ex-Confederates were barred from voting , and several Southern states did not take part in the election . Delegations from Arkansas , Florida , Alabama , North Carolina , Louisiana , and South Carolina were re-admitted during the 40th Congress . President Andrew Johnson held a National Union Convention in hopes of rallying supporters against the Radical Republicans . However , the Republican Party maintained a dominant majority in both houses of Congress , and ultimately impeached Johnson in 1868
death
Assassination of Abraham Lincoln
1866 United States elections