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

Release: Banking and Monetary Statistics, 1914-1941  

Units:  Number, Not Seasonally Adjusted

Frequency:  Annual, 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 1, Table 15 in the original source at https://fraser.stlouisfed.org/scribd/?item_id=6408&filepath=%2Fdocs%2Fpublications%2Fbms%2F1914-1941%2FBMS14-41_complete.pdf&start_page=1

Relevant details can be found in the footnotes of each table as well as the introductory material for Section 1.