The GMT system was initiated in late 1987 at Lamont-Doherty Earth Observatory, Columbia University by graduate students Paul Wessel and Walter H. F. Smith. Version 1 was officially introduced to Lamont scientists in July 1988. GMT 1 migrated by word of mouth (and tape) to other institutions in the United States, UK, Japan, and France and attracted a small following. Paul took a Post-doctoral position at SOEST in December 1989 and continued the GMT development. Version 2.0 was released with an article in EOS, October 1991, and quickly spread worldwide. We obtained NSF-funding for GMT version 3.0 in 1993 which was released with another article in EOS on August 15, 1995. Significantly improved versions (3.1-3.3, 3.3.1-6), 3.4, 3.4.1-5, and 4.0-1.2 were released between November 1998 and May 2006, culminating in the June 2006 introduction of 4.1.3. GMT now is used by 10,000 users worldwide in a broad range of disciplines.