Heyl Royster

Mark McClenathan

Rockford, IL

Joined Firm in 1989

Relying on his Midwestern values and 35+ years of experience, Mark stands ready to fight for his clients.

  • Trucking & Construction Practice Groups Chair
  • Rated AV Preeminent® Peer Review Rating by Martindale-Hubbell®
  • Licensed pilot
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Mark McClenathan

Attorney in Rockford, IL

Mark concentrates his practice on complex civil litigation for the trucking, transportation, and construction industries. Practicing law with Heyl Royster for over 33 years, Mark serves as Chair of the firm's Trucking & Construction Practice Groups.

Mark has defended trucking, construction, manufacturing, aviation, and agriculture businesses extensively in more than 19 county state courts, including northern Illinois and Cook County, and in federal court in the Northern District of Illinois and Wisconsin. He has also handled complex commercial litigation and successfully tried numerous high-exposure construction, trucking, and product liability cases to verdict. He is licensed to practice in Illinois and Iowa and in federal court in Illinois and Wisconsin.

In addition to representing numerous general contractors and subcontractors in building, civil, and road projects, Mark has defended companies and owners in OSHA matters, as well as engineers and architects. Additionally, he has defended farmers, farm service companies and co-ops, and grain storage facilities. He recently defended cases involving chemical spills and spray drift/off-target claims, crop and nursery damage claims, farm equipment accidents, and grain bin fatalities.

Mark is published in construction, contract law, and commercial litigation matters and is a regular speaker on a wide range of topics, including construction, fraud, and contract matters. Mark has served on the Board of Directors and as chair of the Construction Committee of the Illinois Defense Counsel for the past several years.

Mark's strength as an attorney in trucking, transportation, and construction cases comes from his extensive background in mechanics, building construction, and trucking. Mark is a private pilot, owns his own antique auto and engine restoration shop, and is an experienced former farm hand and truck driver. He is involved locally with the Boy Scouts of America and served over the past eight years on the board of trustees of the largest senior retirement community in Northern Illinois.



J.D., Hamline University School of Law

B.A., University of Wisconsin – Eau Claire, magna cum laude

Porter Scholar, Beloit College

Licensure(s) and Admission(s)

State Courts of Illinois

State Courts of Iowa

State Courts of Wisconsin

United States District Court for the Central District of Illinois

United States District Court for the Eastern District of Wisconsin

United States District Court for the Northern District of Illinois

United States District Court for the Western District of Wisconsin

Professional Affiliations

Illinois Defense Counsel

Board of Directors, 2018 – present

Commercial Law Committee, Chair, 2016 – 2017

Construction Law Committee, Past Chair, 2015 – 2016

Illinois State Bar Association

Iowa State Bar Association

Winnebago County Bar Association

Community Involvement

Aircraft Owners and Pilots Association (AOPA)

Antique Automobile Club of America (AACA)

Armed Forces Camp (AFC)

Civilian Rifle Instructor, Wisconsin

Beloit Rifle Club, Volunteer

Boys and Girls Club

Coach (Baseball, Basketball)

Leader, Special Building Projects

Boy Scouts of America

Campmaster, High Adventure

Eagle Scout Board of Review for Glacier’s Edge Council (South Central Wisconsin and Northern Illinois)


Merit Badge Counselor

Troop 620, Troop Leader

Club Sports, General Manager, Youth Travel Teams, Baseball, and Softball

Experimental Aircraft Association (EAA)

Harlem Community Center

Coach, Basketball

High School Coach, Certified Girls’ Fast Pitch Softball

Roscoe Youth Baseball Association

Baseball Commissioner


Tournament Director

Special Projects Coordinator

Wesley Willows

Board of Directors, former Chairman of the Board

Executive Committee Chair

Finance Committee Chair


Special Building Committee

Volunteer Coach, Basketball and Football


  • Elicited testimony from several witnesses and a toxicologist expert to prove that the co-defendant "AIP" (alleged intoxicated person) was intoxicated at the time of the accident from alcohol consumed immediately before the motor vehicle accident and not from drinks served to the AIP the night before at the client's establishment. The co-defendant had lost control of his vehicle due to intoxication (.103 BAC), crossed the centerline, and hit the plaintiff's vehicle head-on, causing severe injuries. While the plaintiff was able to win a verdict against the co-defendant for nearly $1.5 million in compensatory damages plus $500,000 in punitive damages, Mark was able to guide the jury to follow the evidence and law, and make the right call concerning the firm's client, despite the obvious sympathy the jury felt for the Plaintiff. The jury deliberated for less than two hours before returning a unanimous defense verdict.
  • Represented a trucking company at trial in a wrongful death lawsuit in LaSalle County, Illinois, where the plaintiff claimed violations of numerous federal and state trucking regulations. At trial, Mark obtained a defense verdict.
  • Represented transportation companies and their insurers in claims against companies, drivers, brokers, specialty haulers, and repair shops in both personal injury and property damage cases.
  • Represented transportation companies in toxic spills and workplace safety claims.
  • Represented trucking companies in contractual issues involving bills of lading and broker disputes.
  • Represented trucking and other companies in motor carrier regulation matters.
  • Represented civil engineers and highway construction contractors in defense of complex road construction and design claims and alleged road defects (such as failed concrete, pavement markings, and construction signage) leading to personal injuries and wrongful death claims. Mark obtained dismissal of all claims.



“IDC Deposition Academy,” NIU Conference Center, Naperville, Illinois (2023)

Keep on Trucking,” Heyl Royster's 34th Annual Claims Handling Seminar (2023)

“Risk Transfer in Contracts ‘Key Provisions and Remedies You Must Have,’” Heyl Royster’s Avoiding Litigation Part Deux Seminar (2018)

“Liability Protection: ‘How to Prevent the Piercing of the Corporate Veil,’” Heyl Royster’s Avoiding Litigation Part Deux Seminar (2018)

“CyberLiability for Park Districts: How to Build Your Defenses for a Cyber Attack,” IAPD and IPRA Soaring to New Heights Annual Conference (2018)

“Cyber Liability,” Heyl Royster’s Governmental Seminar (2017)

“Best Practices for Minimizing Cyber Liability,” Illinois Association of Park Districts Legal Symposium (2017)

“We Need a New Stadium – If You Build It, Suits Will Come: Construction Coverage Issues,” Heyl Royster's 32nd Annual Claims Handling Seminar (2017)

“Liability Protection: How to Prevent the Piercing of the Corporate Veil,” Northern Illinois Builders Contractors Association (NIBCA) (2016)

“Preserving Electronic Information: Protect your business in the event of a lawsuit or the threat of a lawsuit.” Heyl Royster’s Avoiding Litigation Seminar (Urbana, IL) (2016)

“Staying Out of Litigation: When to Require Liability Waivers,” IAPD/IPRA "Soaring to New Heights" Conference (2016)

“Alternative Dispute Resolution – 'Using mediation or arbitration early to avoid lawsuits later.'” Heyl Royster “Avoiding Litigation” Seminar, Rockford and Peoria (2016)

“Vicarious Liability – 'Why Should I Care?'”  Heyl Royster 'Avoiding Litigation” Seminar, Rockford and Peoria (2016)

“Concealed Carry: Illinois Law in Review,” Heyl Royster's 30th Annual Claims Handling Seminar (2015)

“Discrimination and Retaliation (Civil Rights Act, ADEA, ADA, and other),” Recent Legal Decisions Affecting Businesses & Employers, Heyl Royster Seminar (2015)

“Staying Out of Litigation: When to Require Liability Waivers,” IAPD/IPRA “Soaring to New Heights” Conference (2015)

“New Concealed Carry Law Considerations for Employers,” Illinois Defense Counsel Seminar, Chicago (2014)

“How to Use Technology Advancements in Construction Litigation,” Illinois Association of Defense Counsel and the Illinois Insurance Association Spring Symposium (2014)

“Medical Cannabis: A Primer For Employers and Governmental Entities,” Heyl Royster Lunch & Learn Seminar/Webinar (2014)

“Building Your Community's Future: Best Practices for Local Government Construction Projects," (2013)

“Uninsured and Underinsured Arbitration,” ISBA Insurance Section, Chicago (2011)

“Uninsured and Underinsured Motorist Law Update,” Heyl Royster Claims Seminar (2010, 2011)

“Evidentiary Issues for the Claims Professional” Heyl Royster Claims Seminar (2008)

“Premises Liability Update,” Heyl Royster Claims Seminar (2007)

“Mediation and Arbitration: When, Why & How?” Heyl Royster (2001)

“Various presentations to local realtor company meetings on professional liability issues”

“Evidentiary Issues for the Fire Investigator,” Northern Illinois Arson Investigator Association annual certification meetings


Illinois Supreme Court’s Ruling in Munoz v. Bulley & Andrews, LLC: No Immunity for General Contractor Against Suit Filed by Subsidiary’s Employee,” Illinois Defense Counsel Quarterly (2022)

Crossing the Line: Interference with Business and Contractual Relations,” Illinois Defense Counsel Quarterly Monograph (2017)

"Proposed Law Would Not Allow Counties to Set Standards for Wind-Farms," Heyl Royster Governmental Practice Client Alert (2014)

"Sale of Goods - Disclaiming of Warranties and Consequential Damages," Heyl Royster Business & Commercial Litigation Newsletter (2014)

"Municipal Bankruptcy - Can an Illinois Municipality File for Bankruptcy Protection?," Heyl Royster Governmental Newsletter (2014)

"Protect Your Business - The Three Component Test for Restrictive Covenants in Employment Contracts," Heyl Royster Business & Commercial Litigation Newsletter (2013)

"The Effect of The Illinois Firearm Concealed Carry Act on Municipalities" (2013)


  • 1990 Pro Bono Volunteer of the Year, Winnebago County
  • Leading Lawyer by Law Bulletin Media
  • Meritorious Service Award by Illinois Association of Defense Trial Counsel
  • Rated AV Preeminent® Peer Review Rating by Martindale-Hubbell®
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