This is a mystery series for children in elementary school that focuses on events and people from American history. The earliest books focus on the American Revolution, but I found the books about lesser-known parts of American history more interesting, like the book that is set at the Gracie Mansion and the one about Seneca Village in New York, which no longer exists.
Each of the books features different sets of children and are written by different authors.
Books in the Series:
The Hessian’s Secret Diary (1996)
At the beginning of the American Revolution, a ten-year-old girl named Peggy finds a wounded soldier who may be carrying messages for a spy. By Lisa Banim.
Night Raids Along the Cape (1996)
A boy named Asa struggles to warn people of an impending British attack during the American Revolution. By John F. Waters.
A Secret Party in Boston Harbor (1998)
Young Sarah finds herself caught up in the events of the Boston Tea Party. By Kris Hemphill.
Treason Stops at Oyster Bay (1999)
During the American Revolution, Sally’s family must host British troops, and she finds herself questioning where her loyalties lie. By Anna Leah Sweetzer.

The Ghost of the Gracie Mansion (1999)
The Gracie family of New York City goes to their new country mansion to escape a yellow fever epidemic, but strange things are happening at their new house. By Susan Kohl, illustrated by Ned Butterfield.
The Lost Village of Central Park (1999)
Seneca Village is a community of African Americans and immigrants, but things change for the children who live there and the escaped slaves they’ve been helping when the city decides to take the land to create Central Park in the 1850s. By Hope Lourie Killcoyne.