The Figure For January, 1926 Is The Per Share Value Weighted By Outstanding Shares. Source: F.R. Macaulay, "Some Theoretical Problems Suggested By The Movements Of Interest Rates, Bond Yields, And Stock Prices In The United States Since 1856 (NBER, 1938), Pp.A142-A161; F.R. Macaulay, "The Smoothing Of Time Series, " (NBER, 1931).
This NBER data series m11005a appears on the NBER website in Chapter 11 at http://www.nber.org/databases/macrohistory/contents/chapter11.html.
NBER Indicator: m11005a
Release: NBER Macrohistory Database
National Bureau of Economic Research, American Railroad Stock Prices for United States [M1105AUSM505NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/M1105AUSM505NNBR/, November 28, 2015.