Pieter's grandfather, Samuel, and his great uncle, Johannes, had relocated around 1800 from Krefeld to Amsterdam to set up a bookshop.

That same year he enrolled temporarily in the Civil Service and took a position at the National Archives in The Hague, staying till 1877.

In 1878 he was given a teaching chair in Dutch History at Groningen, which he held till 1883, which was when he switched to his alma mater, Leiden.

By early 1903 he appeared to have recovered sufficiently to resume his work, but the disease then came back and he returned south.

[3] Muller's academic contribution was above all to the history of the Netherlands since independence: his various books on the Dutch Golden Age became standard works.