In 1924, Watlow built its first factory and introduced a line of consumer products, including electric irons and heating pads, under the name of Queen Quality. In 1931 Watlow began manufacturing electric immersion heaters, replacing cumbersome steam pipes and fire-hazardous gas. It began to expand worldwide by 1945.

George Watlow, Louis´s son, joined the firm in 1948 and engineered many new products for the company, as well as equipment to manufacture them. Another son, Louis Desloge, Jr. joined the company in 1963 and was responsible for expanding Watlow´s global sales and distribution network of direct sales engineers and distributors.

The company moved to its location in the Westport area of St. Louis County in 1961 and has expanded several times to its present size of more than 185,000 square feet.

Today the company not only makes electric heaters, but also the sensors and controls. It has expanded into plastics processing, medical, aerospace, semiconductor manufacturing, food equipment and petrochemical products. It employs more than 1,500 people worldwide. It also has opened plants throughout the world and bought out several companies along the way. [St. Louis-Home on the River, p. 294, http://www.watlow.com/about/history.cfm]