The Tualatin Valley is a farming and suburban region southwest of Portland, Oregon. The valley is formed by the meandering Tualatin River, a tributary of the Willamette River at the northwest corner of the Willamette Valley, east of the Northern Oregon Coast Range. Most of the valley is located within Washington County, separated from Portland by the Tualatin Mountains. Communities in the Tualatin Valley include Banks, Forest Grove, Cornelius, Hillsboro, Aloha, Beaverton, Sherwood, Tigard, and Tualatin. History In the early 19th century, the valley was inhabited by the Atfalati, a hunter-gatherer Kalapuyan band that spoke a dialect of Northern Kalapuyan. In the middle 19th century, the Atfalati lived in several villages in the valley, including Chakeipi ("Place of the Beaver", translated by early white settlers as "Beaver Dam"). Early Euro-American settlers called the valley the "Twality Plains", a corruption of the name of the Atfalati tribe. Other early variations included Falatin, Nefalatine, Twalaity, and Quality, with each roughly translated as slow river to describe the Tualatin River, or may translate as land without trees. The valley was one of the earliest settled farming regions in Oregon, as settlers began arriving in 1840. In the spring of 1847, Lawrence Hall filed the first land claim, comprising 640 acres (2.6 km²), at Beaver Dam (later Beaverton) and constructed the first grist mill in the valley. In 1849 Thomas Hicklin Denney and his wife Berrilla built the first sawmill in the Beaverton area, leading to a later boom in the timber industry. The lack of roads connecting the upper valley to the Willamette River quickly became a hindrance to early settlers. In 1850, the Oregon Territory created the Portland & Valley Plank Road Company to build a road through the Tualatin Hills connecting Portland with Beaverton. The road was completed in 1860 after financial setbacks. According to Oregon historian Stewart Holbrook, the building of the plank road was the decisive event that allowed Portland to surpass its rival Oregon City for supremacy as the economic hub of the territory. The railroad was extended into the valley in 1868. The growth of agriculture in the valley was eventually limited in the middle 20th century by the need for irrigation. In 1966, the United States Bureau of Reclamation built the Tualatin Project, bringing additional water to many parts of the valley in the last federal reclamation project in the Pacific Northwest. In the second half