The vote to appoint her was 4-0, with outgoing mayor Bill Widmer absent on a business trip. It was newly seated Councilman Cary Wiest's first vote.
Jerry Carlson was elected vice mayor on a 3-0 vote. He abstained from voting.
Ms. Lewis said a top priority as mayor is to "develop a more collaborative council," one that will function with a collegial and respectful spirit.
Many council observers would agree that a collegial spirit would be a welcome change after years of divisiveness and rancor among council members. But there are differing opinions on whom to blame for that rancor.
Outgoing three-term councilwoman Kathy McKeithen last January publicly accused Ms. Lewis of abusive behavior toward her, and called on then-mayor Widmer to demand more civility at meetings.
Mayor Lewis has also complained of incivility and unethical behavior among council members, and campaigned on a promise to work toward restoring civility to the body.
In remarks made after taking the gavel, she said that she didn't expect council members to vote in lockstep and to always agree on issues, but she urged her colleagues to "put aside personal agendas" as they work for the overall good of the town.
Mayor Lewis acknowledged Councilman Widmer's efforts during his term as mayor, noting that "a lot has been accomplished" over the year.
Mary Widmer, Bill Widmer's wife, read a statement by her husband that provided an overview of council accomplishments over the last 12 months. He cited the replacement of interim staff in many key positions with permanent staff, and improvements in outsourced-services contracts with the addition of efficiencies and concessions.
The list also cited improvements in the use of technology "to boost our efficiencies and openness to the public," including the addition of a search capability on the town's website to allow residents to find information easily; and the installation of wireless Internet connections in the Council Chambers, allowing the public to download agendas and staff reports during meetings to cut down on the use of paper.
Mr. Widmer also cited progress in tackling financial challenges, in the near term as well as long term. In the latter category, he cited the establishment of an irrevocable trust that locks away funds to meet long-term financial obligations for retiree benefits. The fund now has about $1.5 million, he said, adding that the town's off-balance-sheet liability is an estimated $7.5 million.
In her statement, Mayor Lewis also named and acknowledged the work of each of the town's core staff members, beginning with the new city manager, George Rodericks. "I have the utmost confidence in his ability to lead the town," she said.
Calling City Clerk Theresa DellaSanta "the hero of 2012," Mayor Lewis acknowledged her duo roles over the course of nine months as interim city manager and city clerk.
The town begins a new year with "a solid foundation" of staff, she said, calling them "a superb group of professionals."
With last week's tragedy in Newtown, Connecticut, fresh in everyone's mind, Mayor Lewis referred to the mass shooting, noting that the town's collective safety and security "remains paramount," including at the 10 public and private schools within its borders.
Shortly after her remarks, Police Chief Ed Flint swore in the town's newest police officer, Chris Vigil, an Army veteran who served two tours of duty in Iraq, and who worked for five years on the Santa Cruz police force.