"I'm figuring things out right now - which is exciting, awkward, fun, and all new for me," Manning said in an emailed statement. She tweeted a picture of her feet in tennis shoes - with the caption "First steps of freedom!!" - after walking away from the Fort Leavenworth lockup in Kansas.
Manning's immediate plans, including living arrangements, remained unclear. Manning tweeted after then-President Barack Obama granted her clemency in January that she planned to move to Maryland, where she has an aunt. Manning originally comes from Crescent, Oklahoma.
Manning, who is transgender and was known as Bradley Manning before she transitioned in prison, was convicted in 2013 of 20 counts, including six Espionage Act violations, theft and computer fraud. She was acquitted of the most serious charge of aiding the enemy.
Manning, a former intelligence analyst in Iraq, has acknowledged leaking the materials, which included battlefield video. She said she wanted to expose what she considered to be the US military's disregard of the effects of war on civilians and that she released information that she didn't believe would harm the US.
Manning, who was arrested in 2010, filed a transgender rights lawsuit in prison and attempted suicide twice last year, according to her lawyers.
"We can all finally truly celebrate the strength and heroism she has shown in surviving and sharing her truth and life with all of us," Chase Strangio, Manning's attorney with the American Civil Liberties Union, said in today's statement that included Manning's post-release comments.