The Army Nurse Corps was established in 1901. During the Sp Am War Congress authorized the army to hire 1,500 nurses and the army hired over 1,100 women. At this time the nurses were not army members but were civilians called "contract nurses." The book Encyclopedia of United States Army Insignia and Uniforms discusses these nurses on pages 188-89. Some of the footnotes here may lead you to further documentation. WD circular 42, Oct 1898, grants 25 cents/day for rations.
You may want to try the Annual Report of the Surgeon General for 1899.
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