Dear Ms. Terstriep,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located the Station Lists, 1942 - 1953 in the Records of the Adjutant General's Office, 1917-1985 (Record Group 407) and found 27 lists of the Sixth Service Command during WWII. Camp Ellis, Illinois was part of the Army Service Forces, Sixth Service Command. The lists are generally monthly or biweekly. Each list is arranged by type of unit and thereunder in order by unit name or number. The nearest town is listed for each unit. Since the lists have not been digitized, you will need to physically go through the lists for units and where the units were stationed, then look at the records for each unit to determine how many soldiers were assigned to Camp Ellis. We also located 1 series and 7 file units that pertain to Camp Eliis in various record groups. For access to the station lists and these other records, please contact the National Archives at College Park - Textual Reference (RDT2) via email at firstname.lastname@example.org.
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 RDT2. We apologize for this inconvenience and appreciate your understanding and patience.
We hope this is helpful. Best of luck with your research.