Two years before her marriage to Karl Benz, she used part of her dowry to invest in his failing iron construction company.
As an unmarried woman, she was able to do so; after she married Benz, according to German law, Bertha lost her legal power to act as an investor.[3] On 20 July 1872, Bertha Ringer married Karl Benz. As he moved on to a new manufacturing venture, Benz & Cie, he continued to use her dowry as financial support. He finished his work on his first horseless carriage in December 1885. Although Bertha financed the development process, and would hold patent rights under modern law, as a married woman she was not allowed to apply for the patent.
Together they had five children: Eugen (1873–1958), Richard (1874–1955), Clara (1877–1968), Thilde (1882–1974), and Ellen (1890–1973).