The C.G. Conn instrument manufacturing company is known as one of the most successful and innovative band instrument manufacturers in the history of the United States. Many of C.G. Conn's instrument product lines have undergone significant changes throughout the company's history, especially in the brass family. The C.G. Conn tuba product lines are no exception to this company's extraordinary success, and have been significantly redesigned since the company began manufacturing these instruments in circa 1880. This research project investigates the tuba product lines that C.G. Conn manufactured between 1880 and 1940. C.G. Conn designed six different tuba product lines during this timeframe, including an unnamed tuba product line with Stölzel valves, the Wonder Valve line, the New American line, the Wonder Model line, the 20-J, and the 22-J instrumental product lines. These tuba product lines have been investigated using extant publications and patent information because the majority of C.G. Conn's internal records prior to 1970 have been lost. In addition to investigating each of C.G. Conn's early tuba product lines, this project also explores the particularly anomalous design in the top-action valve apparatus of the Conn Wonder Model tuba product line. This anomalous design was implemented in the all of C.G. Conn's top-action tuba and tuba-like product lines from circa 1890-1940. This author's measurements of period instruments and analysis of data taken from these measurements indicates that this anomalous top-action valve apparatus design utilized interchangeable parts with other front-action C.G. Conn tuba product lines.