Trecker was born in Peru, Illinois, where his parents had moved when they came from Germany in 1851. When he was 18, he moved to Milwaukee and entered apprenticeship at the Wilkin Manufacturing Co. which produced saw-mill machinery. After his three-year apprenticeship, he went to work for the Kempsmith Manufacturing Co. in Milwaukee, a pioneer builderof milling machines. At Kempsmith,he met E.J. Kearney, and, in 1898, the two men started Kearney & Trecker, concentrating entirely on milling machines.
Among the firm's early technical innovations were the replacement of the belt drive via cone pulleys with a geared feed box (and later a geared spindle drive), flood lubrication, and power rapid traverse. Kearney, who was secretary-treasurer, died in 1934, but Theodore Trecker ran the company until July 1947.