He was to young to file File a Registration Card for the Draft, so he would not had been drafted. Registration was for men born Sept 1900 and earlier. The war ended Nov 18, 1918 and he just turned 18 6 days earlier. The 1930 census for Charles C Whitmire age 29 b. in Georgia, living in Chattanooga, Hamilton County, TN with wife Myrtle S. and daughter Marian V. First married at age 25 has "NO" written to question if a Veteran of U.S. Armed Forces.
Well here is one for you your family has two sons named Charles. Older one is Charles Andrew Whitmore who filed a WWI card in Walker Co GA b. March 14, 1895. Listed as Charles A. b. Mar 1895 in 1900 census, listed as Anders C. in 1910 census where you Charles is listed as Charles C.. Both in 1930 census living in Chattanooga. Charles A is age 35 with wife Bertha and children. He does has "Yes" to being a Veteran of WWI.
In 1920 census your Charles is still living with mother Effie.