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Mark D. Sullivan


Mark D. Sullivan was born and raised in Michigan. In his youth, Mark's family regularly traveled to Wyoming and other parts of the west for camping, fishing and hiking. These adventures instilled in Mark a deep love of the out-of-doors, and in particular the Tetons. Mark returned throughout his years as a student, and during his early years as a professional, always looking forward to the next trip west.

Mark has been practicing law since 1998. After graduating from law school, he started his legal career with Riverkeeper, Inc., a Hudson River-based environmental organization widely credited with helping protect and restore that great American river. After two years working with Riverkeeper's extraordinary advocates, and after earning an LLM in environmental law by simultaneously taking night classes, Mark took a job with the distinguished New York law firm of Carter Ledyard & Milburn (CLM), in the firm's environmental practice group.

At CLM, Mark had the benefit of a balanced practice. On behalf of developers and public agencies, he helped orchestrate environmental impact review and permitting, and then handled the ensuing litigation to see that projects were approved and built. For public interest clients and individual landowners, Mark fought unwanted development projects, using public advocacy, and, where necessary, litigation to see that those projects were stopped. At CLM Mark learned the power of the media, public opinion and the courts in advancing his clients' interests.


Using these skills, Mark has helped his clients build thousands of residential units, miles of transmission lines, and urgently needed new power plants. Indeed, Mark's work was instrumental in the rezoning of Roosevelt Island and the west side of Manhattan. Conversely, his efforts have stopped unwanted suburban box stores, airport expansions, electric substations, and strip malls.Despite his success in New York, Mark yearned for the open spaces of the west. So, in 2003, looking for new opportunities and a different life for his young family, Mark and his wife Nona moved to Jackson, Wyoming. He continued to work remotely for CLM for the next 3 years, wrapping up several long-term projects. Finally, in 2006, Mark struck out on his own and formed Mark D. Sullivan, P.C. Since forming his own firm, Mark has fought for his clients in a variety of matters from publishing disputes to construction litigation. His clients include ranchers, developers, contractors, authors, environmental groups, homeowners associations, hotels, transportation companies, small businesses, and, of course, individuals.


Mark is happy to be a sole practitioner, working in the place he loves on behalf of clients he cares deeply about. Mark has found new satisfaction helping individuals and small businesses in diverse areas of the law. Mark strives to give his clients responsive, personalized attention, and is fully committed to helping them meet their goals. With his wife Nona and their two kids, Wyatt and Lucy, Mark enjoys the good people and extraordinary places that he has come to know in Wyoming. Mark and his family enjoy spending time with friends floating and fishing on the Snake River, hiking and skiing in the mountains, and camping in the Tetons and other ranges that surround Jackson.

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