The Hall Family Chronicles Series
A series of novels centered on Concord, Massachusetts and the Transcendentalists.
Books in the The Hall Family Chronicles series:
The Diamond in the Window (1962)
Following the clues scratched on a window in their attic Eleanor and Eddy embark on a series of adventures across time and space.
The Swing in the Summerhouse (1967)
When two of their friends disappear from the summerhouse, Eleanor and Eddy know they must break their promise and rescue them.