- OVERVIEW
- EXPERIENCE
- NEWS & EVENTS
INDUSTRIES
PRACTICES
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Education
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Washington University School of Law,
J.D., Order of the Coif
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Washington University in St. Louis,
B.S.
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Admissions
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Illinois
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Missouri
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Affiliations
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American Board of Trial Advocates
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American Bar Association
Litigation, Labor & Employment, and Probate and Real Property Sections
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Theodore McMillian American Inn of Court
Master of the Bench
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Missouri Bar Association
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The Bar Association of Metropolitan St. Louis
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Illinois Bar Association
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The American Bar Foundation
Fellow
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Federal Practice Committee of Eastern District of Missouri
Member and Chairperson, 1988-present
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Committee for Eighth Circuit Judicial Conference
Member, Attorney
Admission Fee Fund Committee
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Federal Magistrate Selection Panel, 1991, 2015
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Representative Clients
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Metropolitan St. Louis Sewer District
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U.S. Bank National Association
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Washington Metropolitan Area Transit Authority
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Recognitions
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Listed in The Best Lawyers in America (by BL Rankings) for Eminent Domain, 2007-2025
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Listed in Missouri & Kansas Super Lawyers (by Thomson Reuters), 2005-2019
Top 50 Women, 2005, 2008-2012
Top 100 for Missouri & Kansas, 2010-2011
Top 50 in St. Louis, 2010-2011
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YWCA of Metro St. Louis - Leader of Distinction, 2015
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Listed in Super Lawyers (by Thomson Reuters) Corporate Counsel, 2008-2014
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Employment
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Thompson Coburn LLP
Partner, 1984-Present
Associate, 1977-1983
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Community
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Boys and Girls Clubs of Greater St. Louis
Board Member, 2008-Present
Board of Directors, Secretary to the Board
Board of Directors, Vice Chair, and Chair, 2016-2018
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Judicial Learning Center
Board of Directors, Secretary, 2008-Present
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The Salvation Army
Chair, Property Committee, 1998-present
Executive Committee, 1996-Present
Chairperson, 2000-2002
Vice Chair, 1998-2000
Treasurer, 1996-1998
Chair, Finance Committee, 1996-1998
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Lutheran Family & Children’s Services
Public Relations Committee to Advisory Board
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Mentor St. Louis
Board Member, Vice Chair
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United Way of Greater St. Louis
Consultant, Court Appointed Special Advocates
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Mary has spent her 40-year career representing major corporations in high-stakes trials and arbitrations.
Mary advises clients on complex disputes of all types, including general commercial litigation defense, real estate and construction claims, labor and employment matters, banking, and railroad real estate. She has tried, as lead counsel, more than 75 jury and non-jury cases to conclusion and is a member of the American Board of Trial Advocates.
A key player in some of the longest and most complex trials in the St. Louis region, Mary developed excellent relationships with judges and opposing counsel. She is frequently asked to join pending cases when parties need an experienced courtroom litigator since she excels at leading trial teams, crafting trial strategy, and coordinating the many moving parts of litigation. Mary is a gifted story-teller, supporting her client's cases through skillful cross-examination of opposing witnesses.
Mary was one of the very first women litigators in St. Louis and a founder of Thompson Coburn's Total Commitment® Women's Initiative. In 2015, Mary's role as a mentor and business leader was recognized by the YWCA of Metro St. Louis with a 2015 Leader of Distinction award. She is also a Life Fellow of the American Bar Foundation.
Mary served on the trial team that defended a regional beverage distributor sued after it challenged a 100-year-old state regulation governing relationships between suppliers and distributers. The case, which raised significant questions about state franchise law, was successfully settled a week into a jury trial. (2014)
Mary successfully tried a case for an Illinois school board in a federal jury trial over an age discrimination suit. (2013)
Mary successfully negotiated a settlement that resolved a dozen lawsuits between multiple railroads and the Illinois Department of Transportation over railroad property taken for the construction of the Stan Musial Veterans Memorial Bridge and related highway projects. (2013)
Mary obtained a judgment for a major banking institution that spared it from making multimillion dollar capital contributions to a large apartment development financed through federal historic tax credits. The same ruling also allowed the bank to sell its limited partnership interests without liability for additional contributions or guaranties. (2011)
In a case of national importance, Mary succeeded in obtaining a temporary restraining order for a major regional transit authority in an action to stop collection of a $40 million-plus payment resulting from the downgrade of investment ratings for AIG, which had provided credit support to the transit agency. The action was the lead case in the nation and watched by municipalities in the U.S. and banks around the world that were equity investors in AIG-backed transactions. The aggregate potential liabilities were over$300 million for the transit agency. Prior to a formal ruling, negotiations between both parties resulted in a private settlement. (2008)
Mary prevailed on summary judgment in Cole County in a case brought by the Missouri Attorney General's Office against a railroad client over the railroad's plans to dismantle an abandoned bridge and use the steel for construction of a new bridge. The ruling was affirmed by the Western District Court of Appeals, and Mary also represented the railroad before the Clean Water Commission, which upheld issuance of a DNR permit for the project. (2007)
News
St. Louis Boys & Girls Club announces plans for youth golf facility at former Superfund site
Missouri Lawyers Weekly honors Mary Bonacorsi as a Women’s Justice Awards winner
Cleaning up a toxic site for the Boys & Girls Club
Mary Bonacorsi named a Leader of Distinction
St. Louis Business Journal covers Thompson Coburn’s work on unique Superfund settlement
EPA, Boys & Girls Club announce $30 million cleanup of Superfund site
Women’s Initiative kicks off 2013 mentoring program
Thompson Coburn obtains Missouri Supreme Court victory for Laclede Gas Company