Source: Simon Kuznets, National Product Since 1869 (NBER), 1946, Table I-17, P. 54
This NBER data series a10040 appears on the NBER website in Chapter 10 at http://www.nber.org/databases/macrohistory/contents/chapter10.html.
NBER Indicator: a10040
Release: NBER Macrohistory Database
National Bureau of Economic Research, Net Capital Formation, Total, In Constant Prices for United States [A10040USA027NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/A10040USA027NNBR/, July 4, 2015.