Rubuta ci gaba don wannan sakin layi - Bayan halartar makaranta da kuma nazarin doka a ƙarƙashin Cyrus Blanchard, Rawson da farko ya yi aiki a matsayin darektan 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 Drury's Bluff
Ka yi haƙuri. 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.