In 1850, Mayer emigrated to the United States, joining his brothers,
Henry Lehman and
Emanuel Lehman, in
Montgomery, Alabama. His brother Henry had left Germany in 1844 and opened a dry goods store named "H. Lehman". His brother Emanuel left Germany in 1847 and joined Henry in his business endeavor, which they renamed "H. Lehman and Bro." With the arrival of Mayer in 1850, it became
Lehman Brothers. As
cotton was the most important crop of the
Southern United States and global demand led to profitable business, the Lehman brothers became
cotton factors, accepting cotton bales from customers as payment for their merchandise. In 1864, the
Governor of Alabama,
Thomas H. Watts, appointed Mayer as a Commissioner to visit and look after the interests of Alabama
Confederate soldiers being held as prisoners of war in the North. Other offers of public position were made to him but he declined. In 1867, Mayer and Emanuel moved the company's headquarters to
New York City, leaving their New Orleans cotton operation (renamed
Lehman, Newgass & Co) in the hands of their brother-in-law Benjamin Newgass (father of British war hero
Harold Newgass). They eventually built their New York operation into an important American
investment bank, which was in operation until its September 2008 collapse. Mayer Lehman was one of the organizers of the
New York Cotton Exchange, the oldest commodities exchange in New York City, and served as its director. Mayer Lehman concentrated on the railroad, land, industrial and mining enterprises of the business. He served as the director of The Hamilton Bank, The American Cotton Oil Company, The Union Oil Company of
Providence, Rhode Island, and
The N.K. Fairbank Company of
Chicago. ==Philanthropy==