Data Apply To Acres Subdivided Within 1931 City Limits. Source: Homer Hoyt, "One Hundred Years Of Land Values In Chicago, 1830-1933" Pg. 479-480.
This NBER data series a02067 appears on the NBER website in Chapter 2 at http://www.nber.org/databases/macrohistory/contents/chapter02.html.
NBER Indicator: a02067
Release: NBER Macrohistory Database
National Bureau of Economic Research, Approximate Number of Acres Subdivided Within 1931 for Chicago, IL [A02067US16980A466NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/A02067US16980A466NNBR/, November 26, 2015.