UK National Archives
The National Archives (TNA) is an executive agency of the Ministry of Justice of the United Kingdom. It is "the UK government's official archive, containing 1,000 years of history". All works by Government officials fall under Crown Copyright, which generally means they will come into the public domain 50 years after their creation (with HMSO stating that this applies worldwide). Over the last few years they have teamed up with Wikimedia to donate thousands of works deemed in the public domain.