Ka kammala wannan magana: Bayan ya je makaranta kuma ya yi karatun shari'a a ƙarƙashin Cyrus Blanchard, Rawson ya fara aiki a matsayin darektan wata makarantar gwamnati. Wannan ya ƙare a watan Yunin 1862, a lokacin yakin basasa na Amurka, lokacin da ya shiga cikin 118th New York Regiment. Ya yi aiki a karkashin Brigadier-General Isaac J. Wistar a Yorktown da kuma Major-General W. F. Smith a
Ƙungiyar Drury ta Bluff. Ya shafe lokaci mai yawa yana aiki a matsayin Babban Clerk na sashinsa ko hedkwatar gidan waya, kuma a wani lokaci yana kula da babban rukunin ma'aikata a ofishin Asibitin Sojojin Amurka a Point Lookout, Maryland. Ya gama aikin soja a watan Yuni 1865.