see the beginings of America.
There may have been settlements elsewhere such as in NC and FL, but the true beginnings of what is considered "American" history start in New England. There's just too much to list in Massachusetts alone ranging from the Old North Bridge in Concord to the textile mill history in Lowell to the Freedom Trail in Boston to Sturbridge Village in Sturbridge, MA. There is such a huge mix of old and new in New England and up and down the east coast. September and October are "fair season" up here-Topsfield Fair in Topsfield, MA is the oldest fair in the country. The weather is usually warm days, cool nights in September and coolish days to cold nights in October. Foliage ranges from dullish in bad years to stunning in the good years. Both months are usually drier than the summer, but you do run the risk of hurricanes anywhere on the eastern seaboard that time of year. I'm a big fan of Gettysburg, DC, and VA (think Colonial Williamsburg) for civil/revolutionary war history and Americana and the Carolinas for their beaches. Can't forget The Lost Colony in NC, arguably as old as or older than St. Augustine, thought to have existed in 1588. The town I live in, Billerica, MA, was incorporated in 1655, and boasts a few small museums. Keep in mind it's going to take you the better part of a week to get out and then the same to get back. You'll have to pick and choose what your preferences are.