Mark B. Weinheimer's Profile Image

Mark B. Weinheimer

Mark’s legal practice is focused in order to provide knowledgeable advice and counsel to a wide array of individuals and family-owned businesses, closely-held companies, and their owners and managers, primarily in the business, real estate and estate planning areas. Mark seeks to develop a mutually attentive and respectful relationship with the firm’s clients. Mark brings to his business and individual clients several decades of relevant and valuable experiences, both as a lender and lawyer. His experience allows him to provide sophisticated advice to business owners on a broad range of issues, transactions and industries, and to appropriately counsel and advise companies and individuals on the particular legal issues and associated risks and potential rewards pertaining to the particular situation.

A large part of Mark’s practice is centered on the immediate and longer-term goals for closely-held businesses, including entities owned entirely by members of the same family. He advises clients on issues pertaining to corporate and real estate transactions, and continues to work with clients as they navigate through their own strategic business and family wealth transitions and succession planning.

A sampling of the diverse array of businesses that are included as clients are agricultural enterprises (grain and livestock production, sales and services, marketing and commodities, grain elevators, river terminals, etc.); transportation and logistics; manufacturing, mining and quarrying; commercial and residential construction; real estate (investors, landlords); banks; restaurants and other retail and service businesses. In addition, Mark’s individual client base includes a range of situations, including company executives and managers with employment and compensation matters, stockholder and other co-owner agreements; the grantors, trustees and/or beneficiaries for family trusts established to provide tax-efficient wealth transfers with an overall business or family wealth succession strategy in place.

From formation to exit strategies, Mark handles transactional matters including entity formation; capital and debt raising; due diligence review and related acquisition or sale strategies; drafting and negotiating transactions, closing, and ancillary deal documents; preparing protective agreements for his clients' interests (including buy-sell, employment, non-compete and non-solicit agreements); negotiating and establishing various lease, development, property management, joint venture and other documents for diverse property-focused firms; and completing mergers, acquisitions, divestitures and other strategic business and wealth protection, transition and succession efforts.

Notable Transactions and Results

  • Negotiated and documented the sale transaction(s) for a number of limestone quarry business(es), in both Illinois and Missouri, and resultant diversification of proceeds for family members and/or distributions to business owners.
  • Coordinated succession and multi-generational estate planning for extensive family business(es) through strategic guidance and documentation for various company, real estate, and organizational planning matters while integrating estate and wealth preservation strategies and goals.
  • Assisted family members in the closure and liquidation of a third-generation, multiple-location Midwest retail business caught in a severe economic downturn with successful resolution of numerous creditor and third-party concerns.
  • Represented and advised a sibling throughout a tax-advantaged business separation (corporate split) for a substantial company owned by two brothers in order for the client to be able to more directly seek certainty via control of ownership and management succession, as well as to allow for independent business success based upon the continuing personal efforts of the client and his immediate family members.
  • Counseled the owners of a Chicago-based start-up company involved in the manufacture, production, and marketing of specialized manufacturing equipment, including owner agreements, capital and debt raising efforts, leasing of facilities, licensing and manufacturing agreements, and world-wide marketing efforts.
  • Worked with a major St. Louis-based construction company to devise and implement an ownership and management transfer from father to son while adapting various related entity ownership agreements to provide the best chance for continued success of the company and other related entities upon retirement of the senior generation.
  • Assisted management personnel within the context of a company wholly-owned by an employee stock ownership plan to provide for the employees’ realization of substantial value that had been built up within their respective ESOP participant accounts through the marketing and ultimate sale of the business.
  • In addition to the above sampling of business transactions, a list of notable results would not be complete without mentioning that a large part of Mark’s practice includes the documentation, implementation and administration of personal and business succession plans for numerous grandparents and parents for the benefit of their family members, involving the transfer, preservation and protection of real estate, business ownership interests or entities, personal property and accounts and assets of all types.

Bar Admissions

  • Illinois
  • Missouri
  • U.S. District Court: Eastern District of Missouri
  • U.S. District Court: Southern District of Illinois


  • Saint Louis University School of Law, J.D.
    Cum Laude
    Staff member, Saint Louis University Public Law Review
  • University of Illinois at Urbana-Champaign, B.S.
    with Highest Honors
    College of Agricultural, Consumer and Environmental Sciences

Professional Associations

  • Illinois Bar Association
  • American Bar Association
  • The Bar Association of Metropolitan St. Louis
  • Agricultural Law Section Council, Illinois State Bar Association – Former Chair
  • Mid-America Tax Conference – Former Planning Committee Member

Community Involvement

  • American Red Cross, Eastern Missouri Region (Greater St. Louis Region) – Board Member
  • Southern Illinois University-Edwardsville School of Business – Former Advisory Board Member
  • Nature Preserve Foundation/Watershed Nature Center (Edwardsville, IL) – Former Board Member

Read more about Weinheimer Opel Law Firm's commitment to the community.


  • Selected by peers as a Leading Lawyer in Closely & Privately Held Business Law
  • Selected by peers as a Leading Lawyer in Agricultural Law.