A few years ago, Kevin Lynch invited a small group of researchers interested in motion planning and control of mechanical/robotic systems to visit Northwestern University. This small, informal meeting gave us an opportunity to discuss our latest ideas and also attempt to bridge some of the gaps between control/mechanical engineering and algorithms/computer science. It was also a nice opportunity to build new relationships and collaborations. The meeting was so valuable to us that we have continued to meet every year. This brings us to the 4th Midwest Mechanical Motion Meeting (M^4) which will be at the University of Illinois at Urbana-Champaign. We plan to have about a dozen researchers describe their current projects and following each presentation will be a discussion. Attendees are also encouraged to come a day early, on Friday, September 6, for lab visits, meetings with other UIUC faculty, and/or socializing with other M^4 participants.