Foster's Home for Imaginary Friends was founded by the elderly Madame Foster to provide a foster home for abandoned imaginary friends.
There are (according to "Setting A President") 1,340 imaginary friends in Foster's Home; however, at the end of "Emancipation Complication," Madame Foster states that there are 2,038 imaginary friends currently residing in the house, plus Bloo and Mr. Herriman, Madame Foster's imaginary friend whom she never outgrew. The house motto is "Where good ideas are not forgotten".