In 1824, the Hudson’s Bay Company placed Dr. John McLaughlin in charge of their Fort Vancouver outpost in the then Oregon territory. Names like Heron, McDermot and Lane claimed Irish ancestry at nearby Fort Nisqually and John Howard and William McCarty both came north with the Ewing-Young party From California in 1834. At about the same time, Patrick James McGowan, a fisherman near Chinook, and farmer William Ryan arrived directly from Ireland. Irish-Americans were among the steady stream of immigrants to cross the Oregon Trail during the "Great Migration" of 1843.

In 1844, the Simmons family arrived from Missouri and settled near what is now the capitol city of Olympia. A miller by trade, Simmons built a sawmill and a grist mill near the Tumwater Falls which he sold in 1850. He was elected Postmaster despite having no formal education and was assigned to be an Indian Agent by then Territorial Governor Issac I. Stevens and was instrumental in the treaties imposed on Native Americans in 1854.

Many Irish women came to America to work as domestic servants. In 1852, Captain Edward Eldridge, met and married Teresa Lappin who was born in County Armagh, Ireland, and immigrated to the United States in 1850, during the Great Potato famine. Eldridge joined with Henry Roeder and settled in what is now Bellingham bay where they founded the first settlement and erected a lumber mill in 1853.

The Irish were prominent among the influx of European and European-American immigrants flooding into the region. After taking possession of the Oregon Territory in 1846, the gold rush of 1848 and subsequent discoveries of gold, silver, lead and coal in Washington congress passed the of 1850, which:

(1). Provided to every settler or occupant of the public lands, American half-breed Indians included, above the age of 18 years and being a citizen of the United States or having made declaration to become a citizen, who shall have resided on and cultivated the same for four consecutive years, the quantity of 1/2 section or 320 acres of land, if a single man, and if married, or shall become married before December 1850, the quantity of one section or 640 acres, one half to himself and the other half to his wife.

 (2). That to all white male citizens of the United States or persons making declaration to become citizens, that between the 1st day of December and 1850 and the 1st day of December 1853, 21 years of age or older is granted 1/4 section or 160 acres of land if a single man; and if married, or shall become married within one year from the time of arriving in the territory, or within one year of becoming 21 years of age as aforesaid, then the quantity of 1/2 section or 320 acres, one half to the husband and one half to the wife.

Because of the provisions of this act, married women were effectively recognized as equal to men, at least in their right to possess land. The act was transitory, expiring in a few brief years, but many took advantage of it and acquired large tracts of land. Between 1853 and 1880, the Irish grew to become second only to Canadians as the largest European Immigrant Group in Clark, King and Walla-Walla counties with 2,243 Irish listed in the decennial census of 1880.

During this time period, the Irish collected around military installations and mining centers. Often the Irish who served as enlisted men remained in Washington and were the leading settlers in remote areas of the state. William O’Leary, from County Cork and Irishman William Medcalf were the first white settlers to farm in Gray’s Harbor near the lower Chehalis River.

The end of the Civil War brought a fresh wave of immigrants to the Pacific Northwest. “In 1867, the Irishman Samuel Benn, bought several hundred acres of government land along the north shore of the Chehalis river and both shores of the Wishkah, site of present day Aberdeen, Washington. A successful dairyman, Samuel and his wife Mary were at the center of the town’s social life.”

North of Vancouver, the farming town of was settled in 1860 by a group of Scots and Irish, as were the towns of Dublin and Ireland.At the opposite end of the state, in what is known as the “Inland Empire”, while comprising only 4.3 percent of the population in the 1880 census, Irish names like Monaghan, Clark, Conlan and Costello are among those listed as business pioneers. These men were instrumental in helping to found and grow a city near Spokane Falls that grew to become a hub of commerce trading goods from surrounding farms and mining communities.