Here are lists of selected large American companies in 1917 and 1929. The notes on the spreadsheet tabs are important to read.
Source: Forbes Magazine 50th Anniversary Issue, 9/15/1967
Largest Companies 1917 and 1929 (XLSX)
In our continuing research, we discovered that the Forbes list for 1929 left out some major public retailers; their data for 1929 is in this picture:
More details on these companies and a spreadsheet can be found here:
