Madison Dearborn Partners, LLC | 18,330 followers on LinkedIn. Madison Dearborn Partners, LLC ("MDP") is a leading private equity investment firm based in Chicago. | Madison Dearborn Partners, LLC ("MDP") is a leading private equity investment firm based in Chicago that, since its formation in 1992, has raised aggregate capital of approximately $31 billion and has completed over 150 investments. MDP seeks to invest in partnership with outstanding management teams to drive growth and achieve significant long-term value appreciation at its portfolio companies and for its limited partner investors globally. A flexible investment approach, encompassing both buyout and growth equity investments, expertise in four dedicated industry verticals and a focus on upper middle market and middle market companies have been and continue to be key tenets of MDP’s investment strategy.