With all the action on the Seacoast , the interior of southern New Hampshire  was neglected for much of the early days of the country. That changed at the turn of the 19th century, when industrialization hit and the textile mills began to pop up practically overnight all over New England.
Of all the rivers in the region, the Merrimack was hands-down the best location for the cotton and textile mills that drove the region’s economy. Not only did it have a fast-running current with lots of waterfalls, but it had lots of trees to drive the furnaces and proximity to Boston  and Portsmouth  for transport of goods. It’s no surprise the Merrimack took off as an industrial powerhouse in the 1800s.
Today, those formerly bustling mill towns are ranged up and down the valley, focused around Manchester —the largest city in New Hampshire and one of the largest in New England. The legacy of the Victorian era survives in the cities’ imposing downtown architecture, even as each of them has struggled to find its groove in the modern era, with varying results.
Driving to Merrimack Valley from Boston , take I-93 north to exit 44, then I-495 south to exit 35, and finally U.S. Route 3 north across the border. For downtown Nashua , take exit 5 off U.S. Route 3 (50 mi., 1 hr.). For Manchester , take U.S. Route 3 north from Nashua to I-293 and take exit 5 for downtown (20 mi., 25 min.). For Concord , take I-293 north from Manchester to I-93, then take exit 14 (20 mi, 20 min.). From the Seacoast  area, take Route 101 west from Hampton  to Manchester (35 mi., 45 min.).
The city of Manchester serves as a secondary air gateway to New England, with flights from many national carriers, as well as Air Canada, arriving at Manchester Boston Regional Airport (603/624-6556, www.flymanchester.com ). The airport is located six miles south of downtown Manchester. All major car rental companies have desks on the first floor near Baggage Claim B. The Manchester Transit Authority (603/623-8801, www.mtabus.org ) runs buses from the airport to the Canal Street Transportation center downtown throughout the morning and afternoon for a fare of $1, taking approximately a half hour one-way. Alternately, you can hail a cab at the airport for a 15-minute ride downtown—fare is about $15.
Amtrak (800/872-7245, www.amtrak.com ) makes stops in Manchester (119 Canal St.) and Concord (30 Stickney St.).
Greyhound (800/231-2222, www.greyhound.com ) runs buses to Manchester (119 Canal St.) and Concord (30 Stickney St.) from around New England. Greyhound also stops in Nashua (30 Elm St.).
Local carrier Concord Coach Lines (603/639-3317, www.concordtrailways.com ) operates a commuter bus down the Merrimack Valley  to Boston . Additionally, for passengers with a same-day ticket for Manchester airport, the Manchester Shuttle (603/624-6539, ext. 324) offers a free shuttle bus from Boston. The shuttle operates daily, 24 hours a day, leaving every other hour from MBTA Sullivan Station on the Orange Line. The trip takes approximately 1 hour and 15 minutes.
The Manchester Transit Authority (603/623-8801, www.mtabus.org ) also runs routes within the city, and a shuttle to Hampton Beach. The Nashua Transit System (603/880-0100 x203, www.gonashua.com ) runs shuttle buses around Nashua. Concord Area Transit (603/225-1989, www.bm-cap.org ) has stops throughout Concord.