For statistical purposes, the United States Census Bureau has defined Alsea as a census-designated place (CDP).

The Alsea area was settled by Europeans early as 1855, when the name "Alseya Settlement" appeared on the Surveyor general's map.

[5] In the early 1850s settlers moved from the Willamette Valley into the Alsea area to take up donation land claims.

[8] This region experiences warm (but not hot) and dry summers, with no average monthly temperatures above 71.6 °F (22.0 °C).

[13] The bridge carries Hayden Road over the river from an intersection with Route 34 about 2 miles (3 km) west of Alsea.