Sam Johnson is a native of Knoxville, Tennessee and earned his degree in Mechanical Engineering from Virginia Military Institute.  He was commissioned through ROTC in May 2005.  After attending the Basic School, he attended Field Artillery Officer Basic Course in Fort Sill, OK.  Upon graduation he was stationed with Headquarters Battery, 2d Battalion, 10th Marines in Camp Lejeune, NC where he served as Platoon Commander, Executive Officer, and Commanding Officer.  In February 2007, LtCol Johnson deployed in support of Operation Iraqi Freedom (OIF) as the Commanding Officer of Headquarters Battery to Camp Fallujah, Iraq.  During this time, Headquarters Battery served as a Provisional Infantry Company and Guard Force for Camp Fallujah.

Upon redeployment in September 2007, LtCol Johnson moved to Battery L, 3d Battalion, 10th Marines in Camp Lejeune, NC where he served as Liaison Officer, Assistant Executive Officer, and Fire Direction Officer.  In August 2008, he deployed with Battery L on the 26th Marine Expeditionary Unit.  While deployed, he conducted training exercises in Italy, United Arab Emirates, and Kuwait.
  
In June 2009, LtCol Johnson assumed his role as Inspector-Instructor and Commanding Officer, Battery I, 3d Battalion, 14th Marines in Reading, PA.  During this time, he co-founded Keystone Wounded Warriors, an Eastern Pennsylvania non-profit organization that seeks to honor and empower injured service members who were wounded on or after 9/11 with connections to the State of Pennsylvania.  He served as director with Keystone Wounded Warriors until 2012, and now serves as an advisor to the organization. 
   
LtCol Johnson re-joined 2d Battalion, 10th Marines in 2013 where he served as a Fire Support Officer and Commanding Officer, Battery G, 2d Battalion, 10th Marines until leaving active duty in 2015.  At this time he joined the Select Marine Corps Reserves serving as the Operations Officer and Executive Officer for 3d Battalion, 14th Marines.  He was selected to his current grade in 2020 and became the 14th Marines Reserve Operations Officer before taking command of 2d Battalion, 14th Marines. 

He began his civilian career as Program Manager for Duke Energy in Charlotte, NC.  In 2018, he transitioned to a National Veteran non-profit, The Independence Fund, as the Chief Programs Officer and promoted to Executive Vice President, focused on assisting catastrophically wounded, ill, and injured Veterans and their families.  

His personal decorations include the Meritorious Service Medal, Navy and Marine Corps Commendation Medal (with combat distinguishing device and gold star in lieu of second award), the Combat Action Ribbon, and the Outstanding Volunteer Service Medal.