Stonehenge has a history of construction and use extending over more than two thousand years, from about 3100 BC to about 1000 BC or later, on the evidence of radiocarbon dates. As an aid to the understanding of the sequence of building, and of the possible astronomical alignments incorporated in each phase of construction, the principal components of each period are summarised below, with the relevant dates corrected according to R.M.Clark (1975), and are illustrated in figs. 1 and 2. A more detailed description can be found in Stonehenge (Atkinson 1979).

The earliest structures at Stonehenge are three pits found during the extension of the car park. Their excavators (Vatcher & Vatcher 1973) believed them to be postholes for massive tree-trunks, although their form and cross-section differ from those of other excavated postholes at Stonehenge. The late C.A. (‘Peter’) Newham suggested that they could have served as astronomical foresights (Newham 1972); but this must be discounted because pine charcoal from two of them has yielded radiocarbon dates of 7180 be ± 180 and 6140 be ± 140 (L.Vatcher, personal communication).