In Pittsburgh, an enormous well of philanthropic dollars flows to nonprofit organizations each year from foundations with billions of dollars in assets. In order, the top four foundations are the R. K. Mellon Foundation, which has more than $3 billion in assets; The Heinz Endowments, with $2.2 billion; Hillman Family Foundations, with around $1.9 billion; and The Pittsburgh Foundation, which helps manage about $1.6 billion.