When the American Revolutionary War officially ended (in 1783) and the British surrendered at the Battle of Yorktown, the colonists were determined to make the end of the war the end of all British influence in America. This is probably why our light switches turn on the other way, we drive on the other side of the road and we follow different measurement systems. This also shows up in the spelling of \bər-ə\.
Burough is a word in its own right, roughly meaning township (it originates from medieval times where it meant a fortified group of houses). When it occurs in geographical names not in the US (yes, that includes Canada) – it is spelt the same way – as “borough”. For instance:
- Scarborough
- Peterborough
- Loughborough
However, when it occurs in US geographical names, it almost always goes “-boro”. Thus, we have:
- Goldsboro
- Hillsboro
- Jonesboro
- Murfreesboro
The only exception is Marlborough, a city located in eastern Massachusetts.
Note: North Attleborough is also in the US, but it has a variant spelling of North Attleboro, so the rule stated above still applies.