A place as steeped in history as the Granite State has to have a living repository for it all, and ours lives in Concord at the New Hampshire Historical Society. The organization has been around since 1823, or about half of New Hampshire's recorded history, and in that time has amassed a massive collection of objects, volumes, and other artifacts from the state's impressive and eclectic heritage. The museum is located at 30 Park Street in an iconic 1911 building that was funded by a gift from Edward and Julia Tuck. (Brief aside - I always loved the intimate and humble feel of the Eagle Square facility that housed the collections from 1995-2014. The Park Street building is far more elegant and magnificent, with a Smithsonianesque feel.)
What do they have? Vintage artwork (including portraits of native sons like Webster and Pierce), indigenous artifacts like an Abenaki canoe, the original eagle from atop the State House dome, and a rare Revolutionary war flag. There's a wealth of information and items about the state's first in the nation presidential primary, as well as thousands of maps, tens of thousands of books, hundreds of thousands of photographs, all preserving and interpreting the varied and vital history of one of America's most interesting and important states. And far from being a static archive, the Society is an active research partner for scholars and authors. The history of NH is kinetic, evolving, and far from finished.
Oh, and did I mention how awesome the museum store is? Get yourself a John Stark bobblehead, an Isles of Shoals jigsaw puzzle, or some Robert Frost poems. Go and visit. It's only seven bucks, but admission is free for kids under 18, students, and active duty military personnel and their families. It's well worth it.