Conversation so far:
Where was Matthew Boulton born?
Matthew Boulton was born in Birmingham, England.
Where did Matthew Boulton grow up?
The business of Matthew Boulton's father, also name Matthew, prospered after young Mathew Boulton's birth, and the family moved to the Snow Hill area of Birmingham.
Did Matthew Boulton have any siblings?
Matthew Boulton was born in 1728, their third child and the second of that name, the first Matthew having died at the age of two in 1726.
What was Matthew Boulton's upbringing like?
The business of Matthew Boulton's father, also name Matthew, prospered after young Mathew Boulton's birth, and the family moved to the Snow Hill area of Birmingham.
Why did Matthew Boulton leave school?
Matthew Boulton became a partner with his father.
Did Matthew Boulton ever start a family of his own?
On 3 March 1749 Matthew Boulton married Mary Robinson. The Boultons had three daughters in the early 1750s, but all died in infancy

Question: When did he marry her?
Self-contained rewrite: When did Matthew Boulton marry Mary Robinson?