The National Park Service has a rather rich collection of maritime history, and a lot of that comes from the state of Massachusetts. Massachusetts has two maritime centric parks: Salem Maritime National Historic Site and New Bedford Whaling National Historical Park. While neither are particularly large parks you can learn a lot from each with simple day visits.
I personally visited Salem Maritime National Historic Site first (back in the summer of 2014), which is convenient because its history begins slightly earlier than New Bedford Whaling’s. Salem Maritime’s visitor center seems rather updated, which helps it to stand out in a city whose history is more known for witches. The main highlights of the park are a full scale replica of the Friendship, a ship from the War of 1812 (Massachusetts maritime collection continues if you go to the Charlestown portion of Boston National Historical Park where the War of 1812’s most famous ship, the Constitution, is stationed), and a gravel pier that goes out a bit into the town’s harbor. There’s a couple of restaurants that overlook the ship and pier so make sure to stop at one of those while you are visiting the park. There are numerous activities that you can do with a ranger at the park, but we did not have time to do those. Walking around the ship and pier was more than enough to make this trip memorable.
I visited the New Bedford Whaling National Historical Park a few years later on a spring visit to Cape Cod. The park doesn’t feel as updated as Salem Maritime’s and to make matters worse there’s an entrance fee to the main attraction, the New Bedford Whaling Museum (which technically is not park of the National Park Service). After a brief trip to the park’s visitor center I made my way to the Seamen’s Bethel (which is the same one from Moby Dick). The park does a great job of establishing Moby Dick and its relationship with real world history as well as the life of the book’s author: Herman Melville. Just like Salem Maritime, this site does not require more than a day visit.
Massachusetts has a surprising wealth of maritime history and the National Park Service does a pretty good job of maintaining it for future generations through numerous sites.