Data Were Obtained By NBER From The Latest Manual In Which They Were Available. Source: National Bureau Of Economic Research; Poor'S "Manual Of Railroads"
This NBER data series a02083b appears on the NBER website in Chapter 2 at http://www.nber.org/databases/macrohistory/contents/chapter02.html.
NBER Indicator: a02083b
Release: NBER Macrohistory Database
National Bureau of Economic Research, Increases In Railroad Mileage for Maine, New Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island, New York, New Jersey, Pennsylvania [A0283BUSA374NNBR], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/A0283BUSA374NNBR/, August 29, 2015.