Salem, Massachusetts is a great travel destination any time of the year. Historic Salem has the Salem Maritime National Historic Site which covers the maritime history of the town as one of the early major port cities in the new world. And of course there is the witch trial history as well.
If there is one time of year to go to Salem it is during the Halloween season. The town celebrates the holiday like nowhere else, one month long party. Save the sightseeing for later just come, mingle and join the party. Check out the web site Haunted Happenings for an up to date listing of activities for the Halloween season. There is certainly no shortage of things to do the weekend before Halloween but my suggestion is to get into costume, wander the streets and join the fun.