Until the 1950’s, civilian ambulances were used primarily to transport patients, not to treat them en route, so car-type models similar to hearses (many cars served as both) were standard. The taller, van- or truck-based ambulance that could carry more equipment and allowed more room for emergency personnel to work replaced the sedan-delivery in the 1970’s. See more at finding aid.
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Memorial Hospital System, "1936 Oldsmobile ambulance, Memorial Hospital" (1936). Library Exhibit Images. 141.