As a young man of 21 in 1858, Moody's work in Chicago led to the largest Sunday School of his time, with 1,500 in attendance weekly. It became so well known that the just-elected President Abraham Lincoln visited and spoke at a Sunday School meeting on November 25, 1860.
After the American Civil War started, he was involved with the U.S. Christian Commission of the Y.M.C.A., and ministered at several battlefields. He was president of the Chicago Y.M.C.A. from 1866 to 1869.
He started a church in Chicago that was burnt down in the Chicago Fire of 1871. It was rebuilt within three months.
It was in a trip to England that he became well known as an evangelist, to the point that some have claimed he was the greatest evangelist of the 19th century. His preaching had an impact as great as that of George Whitefield and John Wesley within Britain, Scotland and Ireland. On several occasions he filled stadiums of 2,000 to 4,000 capacity. In the Botanic Gardens Palace, a meeting had between 15,000 to 30,000 people. This turnout continued throughout 1874 and 1875, with crowds of thousands at all of his meetings. When he returned to the United States, crowds of 12,000 to 20,000 were just as common as in England. President Grant and some of his cabinet attended a meeting on January 19, 1876. His evangelistic meetings were held from Boston to New York, throughout New England and as far as San Francisco, and other West coast towns from Vancouver to San Diego.
He preached his last sermon on November 16, 1899. It has been claimed he was instrumental in winning one million people to Christ, although this is unprovable, due to lack of centralized record keeping.