The Colorado politician was sworn in Tuesday as the nation's first out gay governor.
Thousands watched as Polis took the oath of office beside his partner, Marlon Reis, and their children on the steps of the Colorado capitol in Denver. A rainbow banner, a symbol of LGBTQ Pride, was on the platform below.
Polis also acknowledged the historic nature of his swearing-in.
"I am honored by this great responsibility and humbled by your trust," he told the people of Colorado. "And I must begin by saying I am very conscious of the fact that there were many brave people over the years who made it possible for someone like me to be standing here giving a speech like this.
"I am grateful and forever indebted to those who came before me -- who struggled for equal rights, who stepped up for public service in all its forms, who made difficult sacrifices and worked faithfully toward a brighter future for our state, our nation, and our world."
In his address, the Democrat spoke to the state's diversity and its willingness to embrace change. "Diversity makes our state healthier and more prosperous," he said. "We complement one another, learn from each other, make each other better, and in that work, we respect each other's rights, sharing a common faith in our abilities and our future while having real conversations about how to make progress."
Polis, formerly a congressman and a successful businessman, soundly defeated his Republican opponent, Walker Stapleton, in the November election. He succeeds Democrat John Hickenlooper, who was term-limited, to become the state's 43rd governor. His priorities include universal health care, improving public education, and encouraging the development of clean energy.
Polis is not the first gay man to hold office as a state governor. Former New Jersey Gov. Jim McGreevey was closeted when elected and came out as gay immediately before resigning in 2004 due to an extramarital relationship.
Singer and LGBTQ activist Cyndi Lauper -- who tweeted her support of the new governor -- and the band Nathaniel Rateliff & the Nightsweats are set to perform at Polis's inaugural festivities. The ceremony included a performance from the Denver Gay Men's Chorus.