A reputation as a builder, he built extensivly in the Delta - Piramesse, but mainly at Tanis - enlarging the temple of Amun, adding small triumph scenes of the King smiting his foes (to a shrine east of the tomb of Psusennes I), also the at the South Temple of Khons. South of Memphis it is difficult to find any works dating to Siamun (this is also typical of the rest of the 21st Dynasty however) - there is a graffito dating to Year 17, an entry in the Karnak priestlty Annals records the same date.
It is thought that Siamun was responsible for moving Amenemope to tomb of Psusennes I (removing Mutnodjmet, wife of Psusennes I, at the same time) - although the reason for this is still unknown.
Siamun and the Royal Cache
His name does appear several times, with different regnal years on the wrappings of the later royal mummies from the Deir el Bahri cache (DB320). - In Year 5, Nesikhons (a wife of Pinudjem II) died and was buried (briefly) in the tomb of Inhapi (later moved to DB320). In Year 10 Pinudjem II died and replaced by his son, Psusennes III, this brought about a drastic change in the movements of the royal mummies (up to this point they were still collected in small groups in certain tombs for safety), it was now decided to bury these mummies in a large groups in a tomb (similar to the priests own tombs - Bab el-Gasus) of Pinudjem II (DB320)
His family links are unknown,