Mark C. Pennington is an accomplished attorney with over 35 years of experience in environmental law.

From 2010-2020, he has been listed as a "Super Lawyer" in New York Super Lawyers – Metro Edition magazine. He graduated magna cum laude from Yale University in 1979 with a B.A. in Literature. He received his J.D from New York University School of Law in 1985.

After a clerkship with U.S. District Judge Barbara Crabb in the Western District of Wisconsin, he began his career in environmental law in 1986 with the Washington, D.C. office of Bryan Cave, where he developed an in-depth knowledge of hazardous waste law and regulation, representing trade associations and corporations in rulemaking, permitting, and compliance matters. He moved to Bryan Cave’s New York office in 1987, and from there to the New York office of Morgan Lewis in 1990. At Morgan Lewis, he handled a broad array of projects, including cleanups before local, state and federal agencies; multi-party Superfund proceedings; proactive compliance counseling (solid and hazardous waste, clean air, clean water, community right-to-know); compliance audits; environmental management systems; permitting and enforcement proceedings; litigation of insurance recovery and tort cases; and due diligence and contract negotiation in business transactions.

He created Mark C. Pennington LLC in July 2006 to concentrate on his key interests, and to pursue his passion for land conservation and sustainability. In November of 2007, he joined the law firm of John E. Osborn P.C. as Of Counsel. This affiliation enables him to draw upon the resources of a talented group of senior and junior practitioners with complementary skills.

He is admitted to practice in the State of New York. He is a frequent writer and speaker on environmental law and land conservation issues. He holds a certificate in Accelerated Permaculture Training from the New York Permaculture Exchange.

John E. Osborn P.C. provides strategic advice, contract drafting, troubleshooting, and litigation counsel in complex construction, green building, and environmental projects. Biographies for its lawyers can be found at

Mark Pennington


New York State Bar Association,
Environmental Law Section

New York City Bar
Environmental Law Committee, 1994 - 1996
(chair, subcommittee on Watershed);
Transportation Committee, 1996 - 1998

American Bar Association,
Section on Natural Resources,
Energy and Environmental Law

The Land Trust Alliance
(Professional Partner)

Zoning Board of Appeals,
Hastings-on-Hudson, New York
(Board Member 2011-2014)

Roots & Wings
Sustainability Initiative

Dobbs Ferry, New York
(Advisory Board)