Matanuska-Susitna Valley ( known locally as the Mat-Su or The Valley ) is an area in Southcentral Alaska . It is south of the Alaska Range about 25 m from Anchorage , Alaska . Matanuska-Susitna Valley ( known locally as the Mat-Su or The Valley ) is an area in Southcentral Alaska south of the Alaska Range about 25 m north northeast of Anchorage , Alaska known for producing huge vegetables during a 100-day growing season .