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Mark Diehl Sullivan

Mark Diehl Sullivan

Practice areas:

Litigation, Environmental and Natural Resources, Workers Compensation, Land Use & Zoning, Car Accidents, Corporate & Incorporation, Arbitration

Practice Areas

Licensed since 1998

  1. Litigation: 30%
  2. Environmental and Natural Resources: 20%
  3. Workers Compensation: 15%
  4. Corporate & Incorporation: 10%
  5. Other: 25%
  6. More 



Hourly ($150-250/hour), Contingent (25-40%), Retainer (Sometimes)

Payment Types:

Cash, Check

Attorney Endorsements

3 total 

  • Stephen C Biggs

    Mark is an excellent lawyer and a very amiable person. Our firm worked with him as co-counsel on two cases in Wyoming. Mark has a solid knowledge of the law, is a skilled litigator, is deeply concerned for the well-being of his clients, and is a consummate professional. I would recommend him to others looking for a lawyer to represent them in Wyoming.


    Stephen Biggs Appeals Attorney
    Relationship: Worked together on matter

  • Jessica Rutzick

    Mark gets terrific results for his clients and is a really good person to boot.


    Jessica Rutzick Insurance Attorney
    Relationship: Fellow lawyer in community

Contact Info

Mark D. Sullivan, P.C.

5237 HHR Ranch Road
Wilson, WY, 83014-9210



WYAuthorized to practice law200508/27/2015

Professional Misconduct

We have not found any instances of professional misconduct for this lawyer.

Avvo Contributions

Legal Answers

Work Experience

TitleCompany NameDuration
PartnerMark D. Sullivan P.C.2006 - Present
AssociateCarter Ledyard & Milburn, LLP1999 - 2006
Senior Watershed AttorneyRiverkeeper, Inc.1997 - 1999


Association NamePosition NameDuration
Wyoming Trial Lawyers AssociationN/A2010 - Present
Teton County Bar AssociationN/A2006 - Present

Legal Cases

Case NameOutcome
Meyer v. Hatto, 198 P.3d 552 (2008)Victory
Shaw Construction v. Rocky Mountain Hardware, 275 P.3d 1238 (2012)Victory
RISD v. RIOC, 291 A.D. 2d 40; 735 N.Y.S.2d 83 (A.D. 1st Dept 2001)Victory

See all Legal Cases 


Publication NameTitleDate
New York State Bar Association Journal (cover story)The EPA's New Clean Air Rules2006


School NameMajorDegreeGraduated
Pace University School of LawEnvironmnetal LawLL.M - Master of Laws1999
Pace University School of LawN/AJ.D.1997
Kenyon CollegePolitical ScienceBA - Bachelor of Arts1993