Heyl Royster

Mark McClenathan

Practice Groups:



Business and Commercial Litigation

Casualty/Tort Litigation


Product Liability

Professional Liability

Real Estate

Office Locations:

Rockford, IL

Phone: 815.963.4454

Email Me


Attorneys Author IDC Quarterly Articles in Third Quarter 2021 Issue - 10/05/2021

60 Heyl Royster Attorneys Top 2021 Leading Lawyers List - 08/04/2021

Attorneys Author IDC Quarterly Articles in First Quarter 2021 Issue - 02/24/2021

Attorneys Author IDC Quarterly Articles in Fourth Quarter 2020 Issue - 11/30/2020

67 Heyl Royster Attorneys Top 2020 Leading Lawyers List - 07/30/2020

Attorneys Author IDC Quarterly Articles - 06/30/2020

64 Heyl Royster Attorneys Top 2019 Leading Lawyers’ List - 06/28/2019

Attorneys Author IDC Quarterly Articles - 06/10/2018

Heyl Royster Attorneys Recognized at IDC Annual Meeting - 06/07/2018

79 Heyl Royster Attorneys Top Leading Lawyers’ Latest List - 05/31/2018

Elward and McClenathan Receive IDC Meritorious Service Award - 07/07/2017

60 Heyl Royster Attorneys on Leading Lawyers’ Latest List - 06/29/2017

Seven Heyl Royster Attorneys Author IDC Quarterly Articles - 03/31/2017

Attorneys Author IDC Quarterly Articles - 01/20/2017

Mark McClenathan Featured in Leading Lawyers - 01/19/2017

57 Heyl Royster Attorneys Recognized by Leading Lawyers - 04/22/2016

Firm Attorneys Active in 2014-15 IDC Leadership - 08/28/2014

The Effect of The Illinois Firearm Concealed Carry Act on Municipalities - 07/19/2013

Six Recent NOT GUILTY Verdicts from Around the Firm - 11/08/2012


  • Juris Doctor, Hamline University School of Law, 1987
  • Bachelor of Arts (magna cum laude), University of Wisconsin - Eau Claire, 1984
  • Porter Scholar, Beloit College, 1979-1980

Year Joined Firm




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Heyl Royster



Mark McClenathan (Shareholder)


Mark concentrates his practice in complex civil litigation for the trucking, transportation, and construction industries. Practicing law for over 33 years with Heyl Royster, Mark serves as chair of the firm's Trucking practice group.


Mark has handled cases in state courts in more than 19 counties in northern Illinois (including Cook County), plus Iowa, and in federal court in the Northern and Central Districts of Illinois and Wisconsin. He has over 35 years of experience as a defense attorney and has successfully handed and tried numerous high-exposure trucking, construction, and product liability cases to verdict. Mark has also successfully defended product liability cases involving semi-trucks and trailers, diesel engines, construction and industrial equipment, and machine tools. He has also represented numerous general and subcontractors in building and road projects. 


Mark's extensive background in mechanics, building construction, and trucking gives him a unique perspective and strength in his trucking, transportation, and construction cases. In fact, he owns a complete restoration and machine shop where he rebuilds and restores classic autos, trucks, and tractors when he is not in court. Additionally, Mark is a licensed private pilot and has experience working as a former farm hand and truck driver. 


Before moving to Illinois in 1987, Mark worked for the legal department of the Defense Logistics Agency (Defense Contract Services) of the Department of Defense in Chicago, the legal departments of Land O'Lakes, Inc. in St. Paul, and 3M Corporation in Minneapolis.


Heyl Royster offers a 24/7 Rapid Response Team led by Mark to provide clients and their insurers with instant access to our attorneys and the industry's best and most qualified investigators and experts, who can immediately manage on-scene accident investigations, supervise evidence preservation, take statements, ensure proper drug testing is performed, and interface with law enforcement.

Significant Cases

  • Recently represented a trucking company at trial in a wrongful death lawsuit in LaSalle County, IL 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, repair shops in both personal injury and property damage cases.
  • Represented transportation companies in toxic spills and in 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 claims relating to road construction and design, and alleged road defects (such as failed concrete, pavement markings, construction signage) leading to personal injuries and wrongful death claims. Mark obtained dismissal of all claims.


  • Corporate formations for trucking, construction and manufacturing companies.
  • Financing and leasing transactions
  • Risk mitigation audits
  • Risk Compliance
  • Draft broker agreements, employment agreements, independent contractor agreements
  • Negotiation/representation for transportation (trucking, aviation) real estate developments, zoning, regulations/ordinances


  • “Crossing the Line: Interference with Business and Contractual Relations,” Illinois Defense Counsel Quarterly Monograph (2017) - Download Article
  • "Sale of Goods - Disclaiming of Warranties and Consequential Damages," Heyl Royster Business & Commercial Litigation Newsletter (2014) - Read Article

Public Speaking

  • “IDC Deposition Academy”
    NIU Conference Center, Naperville, Illinois 2023
  • “Risk Transfer in Contracts ‘Key Provisions and Remedies You Must Have’”
    Heyl Royster “Avoiding Litigation Part Deux” Seminar 2018
  • “Liability Protection: ‘How to Prevent the Piercing of the Corporate Veil’”
    Heyl Royster “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 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 “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
  • Click here to view full list”

Professional Recognition

  • Selected as a Leading Lawyer in Illinois. Only five percent of lawyers in the state are named as Leading Lawyers.
  • Winnebago County Pro Bono Volunteer of the Year (1990)
  • Court certified mediator, Winnebago County
  • Meritorious Service Award by the Illinois Association of Defense Trial Counsel
  • Martindale-Hubbell Distinguished

Professional Associations

  • Winnebago County Bar Association
  • Illinois State Bar Association
  • Illinois Association of Defense Trial Counsel (Board of Directors, 2018-present; Trucking Law Committee; former Chair of the Commercial Law Committee and Construction Law Committee)
  • Defense Research Institute

Court Admissions

  • State Courts of Illinois
  • State Courts of Iowa
  • United States District Court, Northern District of Illinois
  • United States District Court, Western and Eastern Districts of Wisconsin

Community Involvement

  • Wesley Willows – Board of Directors, 9 years; Chairman of the Board, 2 years; Finance & Executive Committees – Rockford’s largest and only accredited continuing senior care retirement community.
  • Boy Scout leader – Troop 620 (Roscoe, IL), and Eagle Scout Board of Review (Glacier's Edge Council in South Central Wisconsin and Northern Illinois). Merit badge counselor, Eagle Scout candidate mentor. Past Board of Review Chair; Campmaster, high adventure; Assisted special construction projects and Eagle Scout projects.
  • Private Pilot – Member of AOPA, EAA
  • Beloit Rifle Club – Volunteer: Special Building Projects; Youth Shoot instructor; Matches.
  • Civilian rifle instructor – Annual Armed Forces Camp (AFC) in Wisconsin to train Marine Poolees.
  • Active member in Antique Automobile Club of America (AACA) and other antique car clubs
  • Former High School Coach – 8-year High School (certified) girls' fast pitch softball coach
  • Boys and Girls Club – Former baseball coach and Special Building Projects Leader
  • Club Sports – Former General Manager, coach and assistant coach of various youth travel baseball and softball teams
  • YMCA (Stateline) – Former member of the Special Building Committee, and volunteer basketball and football coach
  • Roscoe Youth Baseball Association – Former coach, baseball commissioner, tournament director and special projects coordinator (parks, buildings, and diamonds)
  • Harlem Community Center – Former basketball coach
  • Swim meet official – (timer, announcer)
  • Lecturer – Multiple high schools, not-for-profit organizations, clubs
  • Active supporter of many other local charities and not-for-profit groups