I am hoping someone might know if or where Individual Income Tax information as far back as 1910 thru to 1918 might be kept and in this particular instance I'd start with Washington State?
Dear Mr. Murphy,
Thank you for your question to HistoryHub. By searching Record Group 58: Records of the Internal Revenue Service and Washington on the National Archives Catalog, we located one relevant group of records that matched the time period in which you are interested: Individual Tax Lists, 1909-1917. These records are located at the National Archives in Seattle, please contact them at seattle.archives@nara.gov for more information regarding these records. Best of luck in your research!