Spring, Summer: Colonial history buffs and curious visitors alike can enjoy exploring the site of the oldest blockhouse in the United States. Situated at the confluence of the Kennebec and Sebasticook Rivers in Winslow, Maine. Fort Halifax was strategically built here to protect English colonial settlements along the Kennebec and was occupied between 1754 and 1756. The view of the of the river valley alone is more than enough reason to take a step back into history. A reconstruted replica can be viewed every year between Memorial Day and Labor Day.