Big box retail is out and big housing is in at Northgate Mall in San Rafael.

Two years after the owner of Marin County’s only enclosed shopping mall announced plans to build the largest Costco in the United States — a 180,000-square-foot store with 30 gas pumps that would have been dwarfed only by the chain’s outlets in Mexico and Japan — the developer has decided to scrap the warehouse retailer in favor of a residential development with a new town center.