The alarm buzzes angrily: it is four o’clock in the morning. Although my body protests, I get up and, a few minutes later, start driving through the darkness. I am not the only one: a line of headlights is slowly moving along the winding road up Cadillac Mountain, the easternmost peak in the United Sates. All of us want to be the first people in America to greet the dawn.

This ritual is one of the “musts” in Acadia National Park, in the northeast corner of Maine. On the flat 1,530ft summit, hundreds have gathered. There are babies and grandparents, children and dogs. As we look east, the star-studded sky over the Atlantic slowly morphs from inky black to deep blue, then charcoal grey and finally, rosy pink. As cameras and phones capture the moment, there is a murmur of appreciation, rather than the American rah-rah I expected.

Cadillac Mountain is the tallest of a score of peaks in this park, which takes up most of Mount Desert Island. On August 25, the US National Park Service (nps.gov) will officially be celebrating its 100th birthday with events around the nation and Acadia, the oldest national park east of the Mississippi River – is having a centenary jamboree of its own this year. What makes Acadia so special for me is the juxtaposition of granite mountains and ocean, dense forest and sandy coves, lakes and tidal pools. An easy five-hour drive from Boston, this is one big adventure playground.

A photo posted by Acadia National Park (@acadianps) on Aug 12, 2016 at 3:45am PDT

I start exploring by bike, pedalling along “carriage roads” that loop up hill and down dale. “About 45 miles of gravel road were designed and built in the early 20th century by John D Rockefeller Jr,” my guide, Lenny, explains. The financier once owned much of the park’s 75 square miles and spent summers here. On these lanes, horses did the work; Rockefeller’s guests admired the scenery in comfort, without building up a sweat – unlike me.

Our 18-mile ride takes us past Eagle Lake, Witch Hole Pond and over – or under – elegant stone bridges. We see maples, aspen, birch and soaring white pines. “The pines were perfect for ships’ masts,” Lenny says. “Back in colonial days, the best were labelled as the King’s Pines and reserved for the Royal Navy.”

He points out wild raspberries and the low-bush blueberries for which Maine is known, plus luminous orange mushrooms. “Hallucinogenic!” Lenny tells me, with a chuckle.

Having given my legs a workout on the bike, the next day it is the turn of my arms. Both stable and easy to manoeuvre, modern sea kayaks are a great way to get out on to the water. I join a small group that includes novice and experienced paddlers, from young teenagers to 60-somethings. Under the watchful eye of our guide, Olivia, we set off from Bar Harbor, the island’s main town. “It’s named after the huge sandbar, right there, just offshore,” she explains. “At low tide you can walk across, but be careful: you can be cut off when the tide turns.”

We skim past diving cormorants, keeping our eyes peeled for harbour seals, porpoises and bald eagles. The wind in our faces stirs up waves and spray. “It’s a challenge now, but will be easier on the way home,” Olivia says, encouragingly. But the weather on the Maine coast can be shifty. In a matter of minutes, the sea mist has rolled in. Offshore, the cries of gulls are punctuated by the lonely hoot of a fog horn. It is all very moody.

We stay close to shore and pull up on the pebbly beach in Cromwell Cove, where Olivia provides a quick geology lesson. Acadia was under a glacier 15,000 years ago. As the ice retreated, it sculpted the landscape, gouging out Somes Sound, the fjord that separates the eastern and western flanks of the island. On the way back to base, with the wind behind us, my fellow paddlers swap stories of what to do in Acadia.

The US National Parks Service turns 100 this month

A student enthuses about her day spent rock climbing: “We wore special shoes that provided traction, so we could Spiderman up.” An older couple recommends the Abbe Museum for its exhibitions about the Wabanaki tribes of Maine. “But that is in busy Bar Harbor,” they add. “We prefer to stay in pretty villages, such as Northeast Harbor and Southwest Harbor, with their galleries and cafés.” And that is what I love about Acadia: holidays can be as energetic or as relaxed as you want.

Maine is all about the simple pleasures. On Mount Desert Island, the small communities come alive in summer. Accommodation is unfussy but comfortable. Clapboard hotels have broad porches, rocking chairs and water views. “Getting away from it all” is no cliché: there is often no television in the rooms and – shock, horror – no signal for mobile phones. As for eating out, the best restaurants are the plainest: lobster shacks.

A photo posted by Acadia National Park (@acadianps) on Sep 11, 2015 at 11:29am PDT

In Southwest Harbor, Beal’s is not only a working lobster and fish pier, but also a restaurant. Wearing a plastic bib, I get down and dirty, tearing a lobster apart with my fingers. Sitting elbow-to-elbow at wooden picnic tables on a warm evening, with a salty breeze off the water, this is the perfect end to a day of soft adventure.

Because lobster is synonymous with Maine, I join up with veteran lobsterman Captain John Nicolai – not to eat the delicacy, but to learn about the lifestyle of these crustaceans. Once aboard the Lulu, we motor out to Frenchman Bay, listening to Cap’n John explaining everything from a lobster’s sex life to how it is caught. Hauling up a trap, he explains the clever, yet simple, design: “The first chamber is the kitchen, the second is the parlour. Once they are in the parlour, they cannot get out.” There are some three million traps in Maine waters and 90 per cent are within three miles of the rugged coast: “That’s because lobsters love rocks.”

Back on land, my final adventure combines hiking with birdwatching. Acadia is on the Atlantic Flyway, so this is a great place for birders. As for where to go, with some 130 miles of trails, the only problem is choice. And that is why I am with guide Rich MacDonald. “Some trails are steep, others flat,” he explains. “And with car parks near the trailheads, you are off straight away.” Our two-mountain hike starts off easily enough, through spruce and red cedar. Then it is up, steeply up. The trail zigzags through cracks in the boulders, with handholds in the granite. Some label this section “challenging”; I call it fun.

Suddenly, we are above the trees and walking along the spine of Penobscot Mountain. “That ank-ank sound is the red-breasted nuthatch,” Rich whispers. “And the high-pitched melodious trill is the cedar waxwing.” At the 1,194ft summit, we savour the vista, before continuing on, down into the saddle and up again, to the crest of the even taller Sargent Mountain. We look down to islands, bays and the narrows that separate Mount Desert Island from the mainland. “On a clear day,” Rich tells me, “you can see for 120 miles.” The sky is deep blue; the sun sparkles on the water; the view is like a tourism poster come to life.

Before heading down the mountain, we start chatting to another hiker, who hails from France. “The Alps may be higher,” he tells me, “but having mountains, lakes and the sea all together – this is truly special.” “So, in Michelin terminology,” I ask, “is this 'vaut le détour’ – worth the detour? ” “Non,” he replies: “Vaut le voyage.”

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Getting there

America As You Like It (020 8742 8299; americaasyoulikeit.com) offers seven-night fly-drives featuring Acadia National Park from £1,240 (based on two sharing). The price includes return flights from London Heathrow to Boston, car hire, two nights in Boston, five nights b&b at the Asticou Inn, Northeast Harbor, as well as kayaking, biking and hiking tours.

Staying there

Claremont Hotel, Southwest Harbor (001 207 244 5036; theclaremonthotel.com) has doubles from $150 (£116) with breakfast. Open May 27-Oct 17.

Asticou Inn, Northeast Harbor (001 207 276 3344; asticou.com) has doubles from $155 with breakfast. Open May 20-Oct 16.

Eating out

Beal’s Lobster Pound, Southwest Harbor (001 207 244 3202; bealslobster.com) serves whole lobsters with traditional sides of corn, coleslaw and biscuits (like scones) for about $20.

Getting around

Acadia’s Island Explorer (exploreacadia.com) is a free bus service that links inns with villages, hiking trails and more. The Bicycle Express shuttles cyclists and bikes to and from Acadia’s carriage roads.

Outdoor activities

Coastal Kayaking Tours and Acadia Bike (001 207 288 9605; acadiafun.com) offers guided and solo trips, maps, trail advice and all equipment. Full-day sea kayaking tours from $74 per person; weekly bicycle rental from $118.

The Natural History Center (001 207 266 9461; thenaturalhistorycenter.com) offers bird-oriented hikes for beginners, families and serious birders with ornithologist Rich MacDonald (from $35 per person).

Lulu Lobster Boat Ride (001 207 963 2341; lululobsterboat.com) leaves from Bar Harbor for two-hour excursions with lobsterman Captain John Nicolai ($35).

Further information

Acadia National Park: nps.gov/acad; Acadia’s Centennial: acadiacentennial2016.org; Maine Tourism: visitmaine.com