Founder of the modern field of social work, Jane Addams initially planned to help the sick and the poor by becoming a doctor, but when health problems prevented her from completing medical school, a two-year journey across Europe and struggles with depression made it clear to her that there were other meaningful ways to help people.
Inspired by accounts of the early Christians, Addams was baptized as a Christian at the age of 26, and sought to embody the easy, democratic spirit of the early Christians in her settlement house, Hull House. However, she chose not to incorporate religion into the institution itself, perhaps because she "eschewed...divisive distinctions," and despite being in sympathy with many groups (among them feminists, socialists, and pacifists, and "social Christians"), preferred not to be "labeled" (Stanford Encyclopedia of Philosophy).
Some controversy surrounds the extent to which Jane Addams' Hull House programs were truly secular. While Addams herself was a firm believer in "Christian humanism" and hoped to spread its spirit, there is disagreement about whether the house itself functioned to spread Christianity or merely the loving spirit that Addams saw in the religion. There is also disagreement about whether Addams saw herself as a Christian.
As to why Addams wasn't a missionary in the traditional sense, many believe her time as a student at the Rockford Female Seminary gave her a distaste for the more formal aspects of the religion and its proselytizers.