Isn't it surprising that the Americans went with a Smaller Gallon than the British Gallon = = Especially with the American usually liking everything Bigger ! ! !
Google search came up with this answer "
Why is the US gallon smaller than the UK?
The gallon originated as the basis of systems for measuring wine and beer in England. The sizes of gallon used in these two systems were different from each other: the first was based on the wine gallon (equal in size to the US gallon), and the second was based on the ale gallon (1.65% larger than the imperial gallon). "