Was only able to find a few Adjutant reports from several states for 1899, but not for the US just individual states. Not sure if this helps. Here are some AGO records or RG94 records that maybe of interest at the national archives. please copy and paste link into your web browser.
Thanks for the information. I also found the state AG's report.
Dear Mr. Pierce,
Thank you for posting your request on History Hub!
If you are referring to the Annual Reports of the Adjutant General of the Army, there are copies of Annual reports of the War Department at HathiTrust that include the annual reports of the Adjutant General (as well as other bureau chiefs) within the published Annual Reports of the War Department. There are multiple years to choose from, to include this copy of the report for the fiscal year ending 30 June 1899, and this copy of the report for the fiscal year ending 30 June 1900.
If it is another type of report you are seeking, please provide more details here on History Hub, or email the National Archives at Washington, DC - Textual Reference (RDT1) at email@example.com. RDT1 has custody of the bulk of the surviving military records from this time period. You also may wish to search the National Archive Catalog.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from RDT1. We apologize for this inconvenience and appreciate your understanding and patience.
We hope this information is helpful. Best of luck with your research!
Thanks for the suggestion it was very helpful.