All Figures Are As Of December 31. The Figure For 1944 Has Been Estimated. Source: U.S. Bureau Of Public Roads, Data For 1904-1939: National Automobile Chamber Of Commerce, "Facts And Figures Of The Automobile Industry", 1933, P. 10; 1939, P. 16; 1943, P. 48. Data For 1940-1944: Public Roads Administration, "Comparison Of Motor Vehicle Registrations, 1940-1944".
This NBER data series a01145 appears on the NBER website in Chapter 1 at http://www.nber.org/databases/macrohistory/contents/chapter01.html.
NBER Indicator: a01145
Release: NBER Macrohistory Database
National Bureau of Economic Research, Automobile Registrations, Total, Truck for United States [A01145USA494NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/A01145USA494NNBR/, November 26, 2015.