A year after business leaders in Seattle helped kill a tax that would have raised an estimated $47 million a year for homelessness and housing, Amazon, Microsoft, Connie and Steve Ballmer and others announced that they were giving more than that amount to build hundreds of homes for homeless people in the Seattle area.

The gifts total $48.8 million and will help build eight buildings for chronically homeless people, who are usually regarded as among the hardest to house. They often have disabilities, serious mental illness and substance-use disorders.

The pledges include a $15 million commitment from Swedish Health Services, Premera Blue Cross and Providence St. Joseph Health last month, and more than $30 million more announced Tuesday. It will go to Plymouth Housing, a Seattle nonprofit developer that operates permanent supportive housing for these individuals, facilities where they have access to health care, social services and treatment.

This is part of a $75 million campaign that will allow Plymouth to essentially double the number of units it operates in Seattle. Amazon and Microsoft each gave $5 million to this campaign. According to Plymouth, this money will help leverage as much as $250 million in public funds for the completion of these buildings.

The Seattle Times’ Project Homeless is funded by BECU, Campion Foundation, Raikes Foundation, Seattle Foundation and the University of Washington. The Seattle Times maintains editorial control over Project Homeless content.

On the same day, Amazon announced it would match its employees’ donations to 20 homelessness nonprofits, for up to $5 million, and that it would give $3 million for affordable housing in Arlington, Virginia, where it is siting its new second headquarters.

“Homelessness and affordable housing are real concerns in Seattle and the Washington, D.C., region,” said Jay Carney, senior vice president of global corporate affairs at Amazon and a former White House press secretary under President Obama.

“As neighbors in both, we made these donations to Plymouth Housing and the Arlington Community Foundation because of their work and progress on housing stability and helping families improve their quality of life.”