Source: Board of Governors of the Federal Reserve System (US)  

Release: Banking and Monetary Statistics, 1914-1941  

Units:  Number, Not Seasonally Adjusted

Frequency:  Monthly, End of Period

This series may have irregularities or important features that are not disclosed here. To see whether this is the case, please consult Part 1, Section 2 in the original source at: https://fraser.stlouisfed.org/scribd/?item_id=6408&filepath=/docs/publications/bms/1914-1941/BMS14-41_complete.pdf&start_page=1#scribd-open details can be found in the footnotes of each table as well as the introductory material for Section 2.