The day after her session with the psychiatrist, she and Chapman became engaged. They chose as their wedding day, Friday, June 13, 1924, the day before Margaret's twentieth birthday, just for fun. They purposely picked a day that most couples would avoid because it was believed to be bad luck. During the honeymoon, Chapman's mother came, uninvited, to the cottage they were staying at. When Chapman was away one day, his mother blurted out that she never wanted to talk to her again because she had taken her son from her. Chapman never stood up to his mother. Despite the problems, Margaret tried to make the marriage work, but by fall of 1926, she knew the marriage was over and she gathered the strength to move away. When Margaret first met Erskine Caldwell, they did not get along very well. They eventually got over each other annoying habits and began to work together, writing books and publishing truths. They wrote You Have Seen Their Faces eighteen months after they returned from Moscow. Also, they wrote North of Danube after returning from Czechoslovakia. When they returned to America after this trip, they were married, on February 27, 1939. They eventually divorced in 1942. .
Margaret was a woman of many firsts. She was the first woman photojournalist for the magazine Fortune in 1929. In 1930, she was the first Western photographer allowed into the Soviet Union. Henry Luce hired her as the first female photojournalist for Life magazine, soon after its creation in 1935, and one of her photographs adorned its first cover. She was the first female war correspondent and the first to be allowed to work in combat zones during World War II. She was one of the first photographers to enter and document the death camps and made history with the publication of her haunting photos of the Depression in the book You Have Seen Their Faces, a collaboration with husband-to-be Erskine Caldwell. She wrote six books about her international travels and was the premiere female industrial photographer, getting her start in Cleveland, Ohio, at the Otis Steel Company about 1927.