There is written evidence that Abraham Lincoln became a Christian in 1839 in Springfield, Illinois during revival services at  the  Methodist Episcopal Church, under  the  ministry  of
James  F.  Jacquess.  In a  fascinating  narrative Rev. Jacquess described  Mr.  Lincoln's  conversion:

The church was filled that morning.  It  was  a good sized church, but on that day all the seats were filled.   I had chosen for my text the words  "ye must be born again",  and during the course of my sermon I laid particular  stress  on  "must".    Mr.  Lincoln  came  into  the  church  after  the  services  had commenced, and there being no vacant seats, chairs were put in the altar in front of the pulpit, and Mr. Lincoln and Governor French and his wife sat in the altar during the entire service, Mr. Lincoln on my left and Governor French on my right, and I noticed that Mr. Lincoln appeared to be deeply interested in the sermon.  A few days after that Sunday, Mr. Lincoln called on me and informed me that he had been greatly impressed with my remarks on Sunday and that he had come to talk with me further on the matter.  I invited him in, and my wife and I talked and prayed with him for hours.  Now, I have seen many persons converted; I have seen hundreds brought to Christ, and if ever a person was converted, Abraham Lincoln was converted that night in my house.