Happy Valley is a city in Clackamas County, Oregon, United States. The population was 13,903 at the 2010 census.According to the United States Census Bureau, the city has a total area of 8.32 square miles (21.55 km2), of which, 8.28 square miles (21.45 km2) is land and 0.04 square miles (0.10 km2) is water. It is a member of thePortland, Oregon metropolitan area, bordering Portland, Clackamas, Damascus, Pleasant Valley, and Sunnyside.
Happy Valley was originally called Christilla Valley, named after the first residents, Christian and Matilda Deardorff. They arrived in 1851 and claimed 640 acres (2.6 km2) on the floor of the valley.The city was officially incorporated in 1965 and remained a small community until the late 1990s, when it was one of the fastest-growing cities in Oregon.