A: Teddington, England, United Kingdom
From November 24 to 27, 1958 the National Physical Laboratory at Teddington, England held the first international symposium on artificial intelligence, calling it Mechanisation of Thought Processes.
The proceedings were published in 1959 by Her Majesty's Stationery Office in London as a two volume set nearly 1000 pages long, also called Mechanisation of Thought Processes. In December 2013 volume one was available from aitopics.org at this link. Volume two was available from the same site at this link.
At this conference John McCarthy delivered his paper “Programs with Common Sense.”(See Reading 11.6.)