A clearer understanding of the Middle Period in the southern San Francisco Bay is now possible as a result of various cultural resource management projects in the Coyote Hills and nearby areas. The review of data from CA-Ala-424 and other nearby sites may help in the resolution of certain long-standing settlement and chronology related "problems" in the local culture sequence. A case in point is the "missing" Phase I Late Horizon component at the Patterson Mound site (CA-Ala-328) which is now recognized as present at other sites in the area. The Middle/Late Period Transition and Early Phase I Late Period occupation at CA-Ala-424 is reviewed. The components and their dating, using Bennyhoff and Hughes' (1983) B1 "short sequence", are discussed in terms of their importance to the understanding of the overall Middle to Late Period culture sequence and implications for local settlement patterns.