When French explorer Pierre Dugua and his 79-member party landed on a small, wooded island in the St. Croix River in 1604, the smartphones held up by tourists nowadays to snap a photo of the historic site did not exist. Nor were there motor boats puttering by or cars whizzing along Route 1 on the mainland in this far eastern corner of Maine.

Dugua promptly named the 6.5-acre island St. Croix (French for cross) for its position just downstream from where two water systems meet, form a cross and eventually flow out into Passamaquoddy Bay. The island also was an ideal lookout to spy and fire at enemy vessels attempting to slip up the St. Croix River.

“This is the beginning of permanent French presence in North America,” Carole Broer, a park ranger at the National Park Service’s Saint Croix Island International Historic Site in Calais, said during a recent guided tour. “Canada and the U.S. share this important history.”

St. Croix Island, which skirts the U.S.-Canada boundary line, is not easily accessible and visits are not encouraged. Over time, the isle’s eastern side has sustained much erosion that is threatening historical and critical archeological features.

“Archaeologically and geologically, it’s fragile,” Broer noted. “The amount of it that has eroded over 413 years is quite alarming.”

Eight miles south of Calais, the Saint Croix Island International Historic Site’s mainland park offers ranger-led tours daily through Columbus Day. The park features an interpretive trail flanked by bronze statues of French settlers and Wabanaki Indians.

As part of her tour, Broer explained how Dugua had stepped forward to lead and finance the 1604-1605 expedition accompanied by French expert navigator and cartographer Samuel de Champlain. The party sought to establish a colony in North America where they would be safe from incursions by the British or Spanish.

French Huguenots had attempted to settle in what is now Jacksonville, Fla., in 1564, but were massacred the following year by the Spanish.

“They didn’t want to get attacked by the Spanish again, and they’d certainly sought to stay out of the eyes of the British,” Broer said.

Known as the father of New France, Champlain also was a writer, artist, naturalist and ethnographer whose journals serve as the primary written account of the 1604 expedition. As an explorer, he sought to forge ties with the Native Americans.

“[Champlain] was very interested in learning and meeting different people, people from different cultures,” Broer said. “He envisioned the French living side-by-side with the Native peoples, not trying to push them away.”

The Passamaquoddy and the new French settlers traded peacefully. When winter approached, the Native Americans warned the French not to stay on the island, according to Native American oral traditions. But the settlers did not heed their advice and found themselves trapped on the island by ice and without any fresh food or water. Nearly half wound up dying of scurvy.

“Basically, it’s a lesson,” Broer said. “Listen to the locals.”

Setting them back even further was the two-month delay of supply ships. When the vessels finally arrived with new recruits, only 44 people remained and half were very ill. The surviving settlers packed up and moved, leaving behind a burial ground and only a few standing structures, to Port Royal in today’s Nova Scotia. For a time, the abandoned island was dubbed “Bone Island.”

In 1613, the British burned the island’s remaining buildings as part of their campaign to purge the French from North America. Only a handful of original artifacts exist from that period. Saint Croix Island was declared a national monument in 1949 and became an international historic site in 1984.

From the mainland, the storied island can viewed from a swath of shoreline consisting of red granite ledges and outcroppings. Called Red Beach, the area also is a good place to cool off and enjoy the sea breeze.

“A lot of locals will just come on down because it might be sweltering in town, and this is the best place to be,” Broer said. “There’s always this pleasant breeze.”

Enjoying the scenic view, visitors can picture Champlain and the other French trading and interacting with the Passamaquoddy and their ill-fated winter on the island.

“The French really did come here,” Broer said enthusiastically. “You’re actually walking in the footsteps of Samuel Champlain.”

The Saint Croix Island International Historic Site, located eight miles south of Calais, can be reached via Route 1. The address is 85 Saint Croix Drive. For more info, call 454-3871 and visit www.nps.gov/sacr.