In 1937 Dr. Mary Leakey excavated Site I, and she discovered evidence of late Iron Age habitation consisting of a series of rough stone enclosures, and a number of burials. This material according to Sutton belongs to the late Iron Age and is probably around 200 yrs old (Sutton, 1987). During the 1937 excavation, Leakey also discovered a much older occupation layer, dating to the Late Stone Age. Several burials were uncovered; this area is today referred to as the "Neolithic mass grave" on signage at the Museum.
Dr. Mary Leakey[1] in 1938 excavated Site II and erroneously associated the Sirikwa occupation layers with the pre-Iron Age material on Site I and at the Nakuru burial site.
In 1943 the unexcavated portions of the site were recognised as important archaeological resources, and the site was gazetted as a national monument on 26 November 1945.
In 1965 more excavations were carried by Ron Clarke on Site II, and the southern burial Site I. After these excavations, a small museum was established in the farm house which was previously owned by Mrs. A. Selfe.
Dr. Onyango Abunje in 1973–74 excavated the area adjacent to Site I, and he discovered mainly late Iron Age materials, which included two Iron Age pits and burial mounded.
In 1986, Dr. John Sutton re-investigated Site II and during this time, the investigation revealed three Sirikwa houses. Dr. Sutton concluded by proposing that Site II is indeed not related to Site II and is Iron Age dating to middle centuries of the second millennium.