Northwest Trek Wildlife Park "officially" began its Annual Fund in late 2005, largely in response to the many friends of Northwest Trek who were making gifts to the park without even being asked. That first year, 100% of the Citizen Advisory Council members made significant gifts to support the Master Plan Update then under way, and all Advisory Council members pledged to support the Annual Fund every year with a gift.

The Annual Fund is distinct from the Animal Sponsorship Program, Northwest Trek Conservation Program (NWTCP) and other ways of giving outlined throughout the Giving section of Trek's Web site. Its primary purpose is to support Trek's immediate priorities that are outside the regular operating budget, thus giving Trek the ability to seize opportunities that might otherwise fall by the wayside.