Sudden Valley is a census-designated place (CDP) just outdoor of Bellingham in Whatcom County, Washington.

Sudden Valley is the second-largest homeowner relationship in western Washington, with over 7,000 residents.^{[citation needed]} There are eleven neighborhood parks, miles of hiking trails in woodlands and along Lake Whatcom, beaches, two pools, sports fields, tennis courts, a basketball court, a recreation middle with full gym, an 18-hole golf course, a library, a haven and more.

Based on per capita income, one of the more honorable measures of affluence, Sudden Valley ranks 97th of 522 areas in the own up of Washington to be ranked.^{[citation needed]}

The Community Association of Sudden Valley began as “the Ranch”. The original owner of the area was Banning Austin. In 1949, Austin sold the estate to Glen and Betty Corning, who named it “the Ranch” and lived there as soon as their children until in 1968 they sold 1,200 acres of property for 1.8 million. The additional owner was Ken Sanwick of Sudden Valley Inc. Sanwick envisioned the estate as “Sudden Valley Undevelopment” and wanted to maintain the natural surroundings while yet incorporating homes into the wilderness. By 1969, the County Commissioners qualified the first plat for 158 lots west of Lake Whatcom Boulevard. The first property owner was Mae Schatz, who bought Division 1 Lot 112 in May 1969.

In the 70’s, the Valley distorted ownership a few times. SunMark Inc. bought out the Sanwick Corporation in 1973, and in 1975 Continental Mortgage Investors took higher than from SunMark as the developer. This was gruff lived, as CMI declared bankruptcy not long after. In December 1976, ownership and rule was transferred to the newly named Sudden Valley Community Association. The owner of SunMark, Roger Ufkes, who happened to be the son of the first property owner, formed the original Board of Directors for the further Community Association. Ufkes served upon the Board for two years in the in front 70’s and is credited for urging property owners to buy the golf course and all its subsidiaries for 1.4 million. The one‐time assessment go forward of $4,000 was voted upon and passed by the residents. From this reduction on, the SVCA held the title to whatever the roads, parks, greenbelt, recreation facilities, marina, airstrip, and the country club. Sudden Valley was well on its showing off to becoming the community it is today.