Major Shannon L. Gross enlisted in the Marine Corps in 2005 after graduating high school. Major Gross attended boot camp at Parris Island, South Carolina from June 2005 until September 2005. Upon graduation, Major Gross was meritoriously promoted to Private First Class. Major Gross subsequently attended Marine Combat Training at Camp Lejeune, North Carolina. Major Gross then attended Personnel Administration school at Camp Johnson, North Carolina. While at MOS school, Major Gross was informed that she was awarded a Naval Reserve Officers Training Corps (NROTC) scholarship, which she had applied for while in the Delayed Entry Program. After graduating MOS school, Major Gross was assigned the 0151, Administrative Clerk, MOS. Major Gross was assigned to Marine Aviation Training and Support Group 21, Naval Air Station Pensacola, Florida, from January 2006 until June 2006, where she pinned on the rank of LCpl. Major Gross was reassigned to the Inactive Ready Reserve to attend college at Jacksonville University in August 2006 with an NROTC scholarship.
Major Gross attended Officer Candidate School during the summer after her junior year of college in 2009. After graduating with a Bachelors of Arts Degree in Political Science in 2010, she attended The Basic School and was assigned 5803, Military Police Officer, MOS. Major Gross attended Military Police Basic Officer's Leadership Course at Fort Leonard Wood, Missouri from January 2011 until May 2011.
In June 2011, Major Gross, reported to the Provost Marshal's Officer, Marine Corps Air Station Iwakuni, Japan. While assigned to Marine Corps Air Station Iwakuni, Major Gross held the billets of Services Officer, Operations Officer, and Deputy Provost Marshal. In May of 2014, Major Gross graduated from the Expeditionary Warfare School (Non-resident Course) in Iwakuni, Japan.
In June 2014, Major Gross reported to 3d Law Enforcement Battalion, Okinawa, Japan. While assigned to 3d Law Enforcement Battalion, Major Gross held the billets of Company Commander, Future Operations Officer, and Battalion Unit Readiness Officer. During this tour, Major Gross supported multiple exercises in the pacific region such as Key Resolve, Ulchi Freedom Guardian, Freedom Banner, Ssang Yong, and Philippine Amphibious Landing Exercise.
In June 2016, Major Gross received orders to attend resident Expeditionary Warfare School, Quantico, Virginia. Major Gross reported to The Basic School, Quantico, Virginia in May 2017. While assigned to The Basic School, Major Gross served as the Counterinsurgency Measures and Combat Outpost Tactical Exercise without Troops Primary Instructor as well as a Warfighting Instructor from May 2017 to March 2018. She then served as a Staff Platoon Commander in Company C 3-18 from March to September 2018, followed by Company Executive Officer for Company B 2-19 from November 2018 to June 2019, and then served as the Future Operations Officer for The Basic School from July 2019 to June 2020. She promoted to the rank of Major in April 2020.
In July 2020, Maj Gross reported to Marine Corps Recruit Depot San Diego. From July 2020 until May 2022, she served as the Provost Marshal for Marine Corps Recruit Depot San Diego. In August 2021, she was selected on the FY22 RS CO Selection Board to assume command at Recruiting Station San Diego in June 2022.
Major Gross' personal awards include Meritorious Service Medal, Navy and Marine Corps Commendation Medal (gold star in lieu of second award) and the Navy and Marine Corps Achievement Medal (gold star in lieu of second award).