Every Infantry Regiment has a "Company A" For WWI the 1st Division had four Infantry Regiments:
16th and 18th Infantry Regiment part of the 1st Infantry Brigade and
26th and 28th Infantry Regiment part of the 2nd Infantry Brigade
Each one of those Infantry Regiments had Companies A-M (minus J) so
1st Battalion was companies A, B,C and D
2nd Battalion is E,F,G and H
3rd Battalion is I,K,L and M
So for 1st Division you would have four Company "A"s
Company A, 1st Bn, 16th Infantry Regiment, 1st Infantry Brigade
Company A 1st Bn, 18th Infantry Regiment, 1st Infantry Brigade
Company A, 1st Bn, 26th Infantry Regiment, 2nd Infantry Brigade
Company A, 1st Bn, 28th Infantry Regiment, 2nd Infantry Brigade.
Hope that helps.
Texas Military Forces Museum
Dear Mr. Malmin,
Thank you for posting your question on History Hub.
In addition to the information provided by the previous poster, the National Archives at College Park, MD has a collection of AEF unit records in Record Group 120 - Records of the American Expeditionary Forces (World War I), 1848 - 1942. These records are arranged under the Division level and are further broken up into regimental level reports. Company reports were generally consolidated and combined with the battalion's reports for each regiment in these files; it is necessary to search the full 1st Battalion report for the information provided by Company A specifically.
For the 1st Infantry Brigade, the 16th Infantry Regiment, and the 18th Infantry Regiment, the series has the following files (Entry P 1241-1):
Box 38: Historical Decimal File - 66.1 -- 1st Infantry Brigade 32.1
Box 39: Historical Decimal File - 1st Infantry Brigade 32.16 -- 2nd Infantry Brigade 11.4
Box 42: Historical Decimal File - 2nd. Infantry Brigade 33 -- 16th Infantry 10.7
Box 43: Historical Decimal File - 16th Infantry 11.4 -- 32.16
Box 44: Historical Decimal File - 16th Infantry 32.16 -- 50.4
Box 45: Historical Decimal File - 16th Infantry 50.4 -- 18th Infantry 11.4
Box 46: Historical Decimal File - 18th Infantry 11.4 -- 33.5
Box 47: Historical Decimal File - 18th Infantry 33.5 -- 37
Box 48: Historical Decimal File - 18th Infantry 37.1 -- 26th Infantry 32.1
For more information on these records and the decimal designations, please contact the National Archives at College Park Reference Branch at firstname.lastname@example.org.
We hope this information is helpful.
The National Archives and Records Administration