"While this historic event may be a first, it is not the last."

The Tomb of the Unknown Solider at Arlington National Cemetery in Arlington, Virginia, recently experienced an all-female guard change for the first time in its nearly 100-year history last month.

All Female Guard Change Tomb of the Unknown Solider
Credit: The Old Guard/Twitter

"On a recent Autumn morning at the Tomb of the Unknown Soldier in @ArlingtonNatl, history was made," the Third U.S. Infantry Regiment, known as The Old Guard, shared on Twitter Friday. "For the first time in the 84-year vigil, on the 30770th day of continuous guarding, an all-female guard change occurred with the 38th Sergeant of the Guard."

"We commemorate the achievements of these trail-blazing Tomb Guards," The Old Guard said in a statement shared on social media. "While this historic event may be a first, it is not the last. With diversity in our ranks, race, gender, or any characteristics will never hinder, but only enhance the execution of our sacred mission."

According to Arlington National Cemetery's website, Tomb Guards, also called Sentinels, are chosen for this "prestigious and highly selective post" only after undergoing rigorous training and a demanding series of examinations.

Tomb Guards march exactly 21 steps down the black mat behind the Tomb, turn, face east for 21 seconds, turn and face north for 21 seconds, then take 21 steps down the mat and repeat the process.  The number 21 is significant because it symbolizes the highest military honor in existence: the 21-gun salute.

The history-making all-female guard change reportedly came just as Sergeant of the Guard, Sgt. 1st Class Chelsea Porterfield, the first woman to hold the revered position, was preparing to take her final walk.

"It wasn't anyone's intent to 'engineer' this event, but we knew an event like this had significant meaning," Patrick Roddy, commander of The Old Guard, told Task & Purpose. "So, in honor of SFC Porterfield's service, and at her request, the schedules were aligned for the first all-woman changing of the guard as part of her last walk."