J. Gresham Machen (1881-1937) helped found Westminster Theological Seminary and the Orthodox Presbyterian Church. His firm stand against modernist, theological liberalism can teach the church much today.

Links of interest:

Christianity and Liberalism by J. Gresham Machen (1923), free ebooks in multiple formats from MonergismJ. Gresham Machen Author Biography (from Banner of Truth)

J. Gresham Machen: The Politically Incorrect Fundamentalist by DG Hart

Re-Thinking Missions (Five Minutes in Church History dealing with Machen’s response to the “Re-Thinking Missions report of 1933 and how it led to the founding of the Orthodox Presbyterian Church)

J. Gresham Machen's Response to Modernism by John Piper (1993 Bethlehem Conference for Pastors)

H. L. Mencken's Obituary of Machen: "Dr. Fundamentalis" 

A Short History of the Life of J. G. Machen by Craig S. Hawkins