"After another anxious four months of waiting, the day has finally arrived. I am looking forward to so much!" Manning said. "Whatever is ahead of me is far more important than the past. I'm figuring things out right now - which is exciting, awkward, fun, and all new for me."
Army officials said Manning will remain on active duty - but will be on leave - as she pursues an appeal of her court-martial conviction, according to Army officials. That means she will not be paid but will be eligible for benefits, including health care, during that time.
Manning, 29, was an intelligence analyst for the Army at the time of her arrest in 2010, when she gained international attention for being implicated in one of the largest leaks of state secrets in U.S. history. The trove of material she provided to anti-secrecy website WikiLeaks - documents known as the Iraq and Afghanistan "War Logs" - included video of a U.S. Apache helicopter opening fire on a group of suspected insurgents in Baghdad. Among the dead were two journalists who worked for the Reuters news agency.
She also leaked documents related to detainees at the military prison at Guantanamo Bay, Cuba, and about 250,000 State Department cables.
Manning has been lauded as a hero by some and decried as a traitor by others, including President Donald Trump. Her lengthy initial sentence and at times severe treatment while incarcerated - she spent long stretches of time in solitary confinement and at one point was made to sleep naked - made her a cause celebre for antiwar and government transparency advocates. Critics, meanwhile, said she put US lives and operations at risk as an attention-getting antic.
Obama commuted Manning's sentence as one of his final acts in office, concluding that she had served enough time. The decision marked a surprising turnaround for the president, who brought more leak prosecutions than the previous administrations combined.
Manning announced after her conviction that she was in fact a woman. Her protracted battle to receive treatment for gender dysphoria at an all-male facility increased her profile in the LGBT community. She emerges from prison as one of the most high-profile transgender people in the country.
"Chelsea is someone who has taken on a great personal risk and tremendous personal cost to do something she thought was in the best interest of the public," said Chase Strangio, a staff lawyer with the American Civil Liberties Union and a well-known transgender activist.
He called Manning "an advocate for herself and others at a time when people wanted and needed a voice for government transparency, for trans rights, for principles of democracy."
The possibility that Manning could become a prominent face in the lesbian, gay, bisexual and transgender rights movement has sparked concern among some, however. Gregory T. Angelo, president of the Log Cabin Republicans, an organization advocating for LGBT conservatives, said he finds it "perplexing" that Manning would be idolized.
"I think that it is great that Chelsea Manning is going to be able to live her life authentically, and she should most definitely be allowed to do so, but that does not excuse past behaviors that put lives at risk and put her into prison in the first place," Angelo said. "There are far better representatives of the LGBT community."
That Manning will speak out publicly now that she has been released seems a given. While in prison, she wrote a column in the Guardian newspaper, maintained a blog and posted to Twitter with the help of supporters, who took her dictation over the phone. Her writings touched on issues including the ethics of solitary confinement and the Orlando nightclub shooting, but it also detailed her efforts to gain access to gender-related treatment recommended by her doctors.
In 2014, a federal judge granted her request to formally change her name to Chelsea Elizabeth Manning. The Army also eventually allowed her to use makeup and receive hormone therapy. But it denied a plea to let her grow out her hair, which, according to photos posted on the GoFundMe site, remains trimmed into a side-swept, masculine cut.
Manning's attorneys disclosed in September that she had been approved for gender reassignment surgery. The assurances from the Army that she could have the procedure came two months after Manning tried to commit suicide, and after a hunger strike that lasted four days, the ACLU said. Her sentence was commuted before that surgery could take place.
In the weeks leading up to her release, Manning's Twitter account has counted down the days. On April 20: "You know you've been in prison for a while, when the prospect of freedom is nerve wracking. =|" And just Monday was the message, "Two more days until the freedom of civilian life ^_^ Now hunting for private #healthcare like millions of Americans =P".
"I personally would love for Chelsea to sit on a beach for a month and sip whatever drinks she likes to sip and relax," said Evan Greer, campaign director for Fight for the Future, a digital rights organization, who has been helping to raise money for Manning's return.
But Manning, whom Greer considers a friend after speaking with her over the phone almost every week, is "an incredibly driven person, and I would expect that we will be hearing from her in her own voice," he added.
