A wagon party headed by Arthur A. Denny left Cherry Grove, Illinois on April 10, 1851. The party included his father, stepmother, two older brothers who settled in the Willamette Valley of Oregon, his younger brother David Denny, his wife, Mary Ann Boren, Mary's younger sister Louisa, and their brother Carson Boren. Mary Ann was Arthur Denny's wife and his stepsister. She was pregnant throughout the journey. Mary's sister Louisa Boren married David Denny in 1861. Arthur Denny is said to have been ill throughout the journey, but remained the group's leader.
On July 6, 1851, they battled Indians at American Falls on the Snake River, but escaped unharmed. The following day they met John Low, and he joined the party. Late in July they reached the Burnt River in eastern Oregon where they encountered a man named Brock. He suggested to Denny that Puget Sound would be a good place to create a town.
The Denny Party arrived in Portland, Oregon on August 22, 1851. Arthur Denny was ill and Mary Ann was about to give birth so the party convalesced in Portland. On September 2, Mary gave birth to a son, Rolland H. Denny.
John Low and David Denny headed north to scout the possibilities. Along the way they were joined by Leander "Lee" Terry. In newly founded Olympia, Washington, they met Michael Simmons, wealthy founder of Tumwater, Washington, who guided them to Alki as a possible site for a settlement. On September 28, 1851, Terry and Low began building a cabin with help from the local Indians, and then staked claims to the land. Low returned to Portland to alert the others, Terry looked for a froe to make redcedar shake shingles, and David Denny stayed on in the unfinished cabin. Like his brother, he was not in good health, and his situation was not improved by staying in an unroofed cabin. Then he injured his foot with an axe.
In Portland, Arthur Denny recruited Illinois farmer William Nathaniel Bell and his wife, and, by coincidence, Charlie Terry, Leander Terry's older brother. The Terry brothers, from Waterville, New York, had come west as part of the California Gold Rush, but had not liked the rough and tumble of San Francisco.
On November 5, 1851, the Denny Party left Portland on the schooner Exact bound for Puget Sound and the Queen Charlotte Islands. The Exact carried a number of settlers bound for Puget Sound in addition to the Denny Party, including Daniel Bigelow who settled in Olympia. After a difficult passage, particularly hard on the still-ill Denny, they arrived at Alki November 13, where David greeted them with the words, "I wish you hadn't come."
Denny was bitterly disappointed that Low and Lee Terry had already staked the relevant claims for Alki. However, he had no choice but to pitch in, finish the cabin and settle in for the winter. Denny convinced Bell and Boren that they needed to scout a different location. Once the worst of winter cleared, Denny and sometimes other party members went exploring as far as Commencement Bay (now the site of Tacoma), Port Orchard, Smith Cove, and up the Duwamish River to the present site of Puyallup, before settling on an island in the mudflats near the east shore of Elliott Bay, now the site of Pioneer Square.
For the next three years Alki Point and Elliott Bay sites competed as rival townsites. Charlie Terry bought out his brother and Low's Alki holdings, and led this community. Arthur Denny settled at Elliott Bay and, along with his rival "Doc" Maynard, led nascent Seattle. The tides at Alki were so strong that piers could not be built. Terry moved to the community on the east shore of Elliott Bay, which became the nucleus of the city of Seattle.
Today at Alki Beach, you can see a monument inscribed with the names of all members of the Denny Party.