In 1878 Wells went into the street railroad business with his father. He became superintendent of the Olive and Markets Horse Car Lines. In the late 1800s he was active in the management of the St. Louis Agricultural and Mechanical Fairs held at Fairground Park. He became the first president of the American Steel Foundry Company, organized in 1894.

Rolla Wells was elected and inaugurated in April, 1901. On taking office Wells sold his local public utility holding company and steel stock, so that there could be no 'conflict of interest' involved in his administration. 'New St. Louis' was the slogan of his administration. He headed the City's Government during the Louisiana Purchase Exposition, known as the St. Louis World's Fair of 1904. In this capacity he welcomed visitors to the City from all over the world.

It was during Wells' administration that the City Water Department accomplished clarification of the water supply. Previously St. Louis had been known for its cloudy drinking water. Milk of lime was used with iron sulphate in the first attempts to clarify the water by means of chemical coagulation. This process, then in experimental stage, was introduced in the Spring of 1904. This progressive step was highly desirable at the time because the World's Fair was about to open and bring many visitors.