How does a novel artifact become a mainstream device? Three case studies on the transition from muscle to motor power indicate that the transfer of practices from old to new technologies facilitates technological change and diffusion. Case One examines the horseless carriage industry in the United States during the first decade of the twentieth century. To understand manufacturers' efforts to generate consumer demand, this study reflects upon printed advertisements, manuals, and social commentaries prior to mass production of the automobile. Case Two examines motorization in a highly resistant environment--the post-WWI US Cavalry. Cavalry service and drill regulations manuals serve as the basis for understanding the centrality of the horse to the cavalry's fighting strategy and the cavalryman's identity as a combatant. The Cavalry Journal, an internal military publication, provides evidence of the role military horse culture played in impeding--and eventually facilitating--motorization. Mechanisms employed to maintain equine traditions gave birth to the jeep. The use of the jeep under battlefield conditions replicated cavalry style maneuvers and fighting principles. Similar to the cavalryman and his warhorse, the American GI and his jeep became inseparable. Case Three addresses the domestication of the jeep in the Philippines, where successful motorization was again attributable to horse culture. Photographs, paintings, and observations from travelers, including the Philippine Commission Report of 1900-1901, and contemporary accounts and reflections of local scholars supplemented with phone interviews conducted in the Ilocano and Tagalog (Filipino) dialects prove useful sources for understanding the influence of horse legacy on motorization. Results show that in each case the shift from muscle to motor power required a forced likeness between the motorcar and the horse. Automotive ubiquity did not occur simply because cars became much cleaner, more efficient, and more affordable than horses. In each case, the motorcar relied upon society's long-standing working relationship with the horse in order to be understood and accepted. When cars began to be perceived as functioning like horses, rapid diffusion ensued as socioeconomic and cultural practices built around the horse were transferred to the motorcar.