Rallies are planned from St. John's to Victoria on Thursday calling for an appeal of the verdict.
Gladue, 36, was a Cree mother who lived in Edmonton. Found dead in an Edmonton hotel room in June 2011, she had bled to death from an 11-centimetre wound in her vagina.
The defence for Barton, a long-distance trucker from Ontario, argued the wound was the result of rough sex, while the prosecution said it was inflicted with a weapon.
On March 18, a jury found Barton not guilty of first-degree murder, as well as of manslaughter.
"People I have spoke to across the country are just in dismay that somebody could dismiss a life like that," Lynda Budreau-Smaganis told CBC's The Current.
Budreau-Smaganis is a Cree Métis elder from St. Paul, Alta., who supported Gladue's family throughout the trial.
"The family is really grateful that people care. When you lose a child and it's dismissed that she had no value, it just harms you," she said.
Fawn Lamouche was invited by a friend to demonstrate at the courthouse during the trial, in support of the family.
"When I saw how much pain Cindy's family was in, especially her mom and daughters, I was really impacted," said Lamouche.
After the verdict was handed down, Lamouche felt compelled to do something, so she set about organizing a rally in Edmonton where supporters could sign letters calling for an appeal of the verdict.
"A lot of us have had enough of the justice system failing us," said Lamouche.
Shortly after, people in other cities joined Lamouche's call, and organized rallies of their own. Through social media the rallies have been planned for the same day, April 2.
Edmonton's rally will take place at noon at Churchill Square, across from the courthouse.
Toronto organizer Audrey Huntley called the verdict horrifying and outrageous. She said the dehumanizing treatment of Gladue by the court is what drove her to do something publicly.
Huntley is the co-founder of No More Silence, an advocacy group that raises awareness of missing and murdered indigenous women.
Toronto's rally will take place at noon ET at the Ministry of the Attorney General's office.
The defence lawyer in the case, Dino Bottos, told CBC News that he understands the aboriginal community's reaction. Many people, he said, have the simplistic belief that "he was a white male and he must have got off because she was an aboriginal prostitute."
Very few people showed up for the trial, he said.
"All of these protesters, I have to say, with the greatest of respect, were not in the courtroom."
There were no aboriginal jurors for the trial.
"Juries are supposed to be a cross-section of your peers from society," said First Nations lawyer Will Willier. "So what has transpired here is that we have nine men, two women, one Asian person and one black person, but no aboriginal people so they don't really understand or empathize or identify with Cindy Gladue."
"Had they identified or understood her better, the verdict may have been different."