A protected city landmark on the edge of RiNo that was used for child care for nearly a century is being marketed for sale by its nonprofit owner. Catholic Charities put its building at 1128 28th St. — dubbed the Margery Reed Mayo Day Nursery — up for sale last month, asking $6.35 million. The 25,000-square-foot structure was built in 1926 and is named after the daughter of the center’s original operator, Mary Reed, who died while it was under construction.