His controversial tenure as sheriff brought Arpaio national headlines for massive roundups of suspected illegal immigrants and for the way he ran the Maricopa County jail.
Trump's statement announcing the pardon praised Arpaio for his "life's work of protecting the public from the scourges of crime and illegal immigration", carrying forward themes from a presidential campaign that opened with description of Mexican immigrants as criminals and rapists.
Arpaio thanked the president on Friday night for the decision. This would have involved an FBI background investigation on Arpaio and could have taken months or even years.
Earlier Wednesday, Arpaio appeared on conspiracy theorist Alex Jones' show and thanked Jones for playing a pivotal role in getting Trump to consider a pardon for the former sheriff. Critics of this pardon of Arpaio point out that it did not go through the ordinary Department of Justice process, which is a complicated one, and the department's pardon office has not yet been appointed a leader under Trump. "After more than 50 years of admirable service to our nation, he is (sic.) candidate for a presidential pardon".
Many of them also liked the tactics of Arpaio, who called himself "America's toughest sheriff", regularly held immigrants past their court-ordered release dates and, like Trump, questioned the legitimacy of President Barack Obama's birth certificate.
"Once again, the president has acted in support of illegal, failed immigration enforcement practices that target people of color and have been struck down by the courts".
"There's nothing that can be accomplished by finding Sheriff Joe guilty and putting an 85-year-old man in jail", said Vera Anderson, 76, a Republican organizer and activist in Phoenix. "The pardon was a sign of pure contempt for every American who believes in justice, human dignity and the rule of law".
Pending his scheduled sentencing hearing October 5, Arpaio faced a maximum of up to six months in prison.
During the rally on Tuesday, Trump characterized Arpaio as a victim and asked rhetorically, "Was Sheriff Joe convicted for doing his job?".
"President Trump pardoned a terrorist tonight". "We need him and I feel sad how they're trying to destroy him".
He operated an outdoor "tent city" in which inmates lived in tents, including during periods in the extreme Arizona summer heat.