The very first semi-detached cottages were built in Britain by Joseph Damer, an 18th century Earl who employed Capability Brown as architect. The Shaws, a father and son architectural partnership later made them popular in London in the 19th century. They are now common in Britain, Ireland, Australia, in parts of Canada, and other commonwealth countries like Malaysia.
One doesn’t normally associate the US with semi-detched houses, but I was surprised by "Dayton Doubles" in the MidWest Blog.
One of the earliest, from about 1830
At the turn of the 20th Century
Pre World War 2
Post War Suburbia
1988 Neo Vernacular