Before the Lewis and Clark Expedition of 1805, few Europeans or European-Americans had visited the Sandy River basin.
One of the first documented visits to the upper Sandy occurred in 1838, when Daniel Lee drove cattle from the Willamette Valley to Wascopam via the Indian trail over Lolo Pass.
By 1840, pioneers were using the trail to cross the Cascades, and the Barlow Road, following another old trail, opened in 1846.
One of its branches ran along the Devil's Backbone, a ridge separating the Sandy and Little Sandy basins.
A few of these newcomers settled along the Sandy River.

In 1886, the Portland Water Committee, predecessor of the Portland Water Bureau, began a search for a superior drinking water source.
The committee, led by Henry Failing, commissioned Isaac W. Smith, an engineer and surveyor, to inspect any viable water supply in the region.
Smith chose the Bull Run River, and a five-month survey trip led him to conclude that a gravity-flow system could deliver clean water from Bull Run to Portland.
In 1892, U.S. President Benjamin Harrison signed a proclamation creating a protected area, the Bull Run Reserve, in the watershed.
By 1895 Portland had built a diversion dam on the Bull Run River, and completed its first conduit (Conduit 1) to carry Bull Run water to the city.
At about the same time as the Smith survey, a small farming community, at first named Unavilla but renamed Bull Run in 1895, grew up near the confluence of the Bull Run and Sandy rivers.
Meanwhile, improvements to the Barlow Road encouraged population growth along the lower Sandy and the establishment of cities like Gresham and Sandy.
Even so, by 1900 much of the upper Sandy basin was still remote, wild, and accessible mainly by trails.

Expanding the system's storage and delivery capacities in stages, the city built Conduit 2 from Bull Run to Portland in 1911, and in 1917 constructed a small dam at the high water outlet of Bull Run Lake.
In 1921, the city replaced the headworks diversion dam with a new one, about 40 feet (12 m) high, and added Conduit 3.
In 1929, Portland built Dam 1 (the Ben Morrow Dam), which is about 200 feet (61 m) high.
To keep pace with population growth and increasing water demands, the city created Reservoir 2 behind Dam 2.
The new dam, completed in 1962 at the site of the headworks dam, is a rockfill structure, 110 feet (34 m) high.
By that time, the city had already replaced the aging Conduit 1 with Conduit 4.
Before the Lewis and Clark Expedition of 1805, few Europeans or European-Americans had visited the Sandy River basin. One of the first documented visits to the upper Sandy occurred in 1838, when Daniel Lee drove cattle from the Willamette Valley to Wascopam via the Indian trail over Lolo Pass. By 1840, pioneers were using the trail to cross the Cascades, and the Barlow Road, following another old trail, opened in 1846. One of its branches ran along the Devil's Backbone, a ridge separating the Sandy and Little Sandy basins. A few of these newcomers settled along the Sandy River.
In 1886, the Portland Water Committee, predecessor of the Portland Water Bureau, began a search for a superior drinking water source. The committee, led by Henry Failing, commissioned Isaac W. Smith, an engineer and surveyor, to inspect any viable water supply in the region. Smith chose the Bull Run River, and a five-month survey trip led him to conclude that a gravity-flow system could deliver clean water from Bull Run to Portland. In 1892, U.S. President Benjamin Harrison signed a proclamation creating a protected area, the Bull Run Reserve, in the watershed. By 1895 Portland had built a diversion dam on the Bull Run River, and completed its first conduit (Conduit 1) to carry Bull Run water to the city. At about the same time as the Smith survey, a small farming community, at first named Unavilla but renamed Bull Run in 1895, grew up near the confluence of the Bull Run and Sandy rivers. Meanwhile, improvements to the Barlow Road encouraged population growth along the lower Sandy and the establishment of cities like Gresham and Sandy. Even so, by 1900 much of the upper Sandy basin was still remote, wild, and accessible mainly by trails.
Expanding the system's storage and delivery capacities in stages, the city built Conduit 2 from Bull Run to Portland in 1911, and in 1917 constructed a small dam at the high water outlet of Bull Run Lake. In 1921, the city replaced the headworks diversion dam with a new one, about 40 feet (12 m) high, and added Conduit 3. In 1929, Portland built Dam 1 (the Ben Morrow Dam), which is about 200 feet (61 m) high. To keep pace with population growth and increasing water demands, the city created Reservoir 2 behind Dam 2. The new dam, completed in 1962 at the site of the headworks dam, is a rockfill structure, 110 feet (34 m) high. By that time, the city had already replaced the aging Conduit 1 with Conduit 4.
Bull Run River (Oregon)