Hundreds of onlookers packed City Hall to watch Ed Murray and Kshama Sawant take the oath of office.
"We are not here to celebrate the political victories of individuals, but the persistent values of this city, values that transcend our divisions but bind us together and define us as one people we are heirs of a special progressive legacy," Murray said. "I stand here today the beneficiary of that proud inclusive tradition."
Sawant also became the first socialist to serve in office in modern times, taking her oath on Monday and serving in her first city council hearing.
Bolstered by a grass-roots campaign that harped on economic inequality, Sawant toppled a 16-year incumbent in the last election. The 41-year-old community college professor campaigned on raising the minimum wage in Seattle to $15 an hour and taxing millionaires.
Throngs of supporters crowded a ceremonial swearing-in at city hall, cheering when she promised to work to raise the minimum wage and tax the "super-rich" to fund transit.
"Join with us in building a mass movement for economic and social justice for democratic socialist change where by the resources of society will be harnessed not for the greed of minority but for the benefit of all people," Sawant said.
Sawant says that Seattle is home to successful corporations, but that the lives of working people grow more difficult with rising rents and stagnating wages.