Girls of Friendly Terrace (or Peggy Raymond's Success) by Harriet Lummis Smith

Peggy Raymond and her friends, Amy, Priscilla and Ruth, encounter a new neighbour, Elaine, and her family. While Peggy, in her usual cheerful and practical manner, welcomes them into the neighbourhood of Friendly Terrace, a variety of mysteries slowly unfold about them and why they ended up moving there. (Harriet Lummis Smith later went on to write four sequels to Eleanor H. Porter's "Pollyanna" books.)