US/Canadian border - highway numbers

[Chris]

Many US routes keep the same number once they cross the Canadian border, rather interesting I think.

Washington:
US 97 becomes BC-97
US 395 becomes BC-395

Idaho:
US 95 becomes BC-95

Montana
US 93 becomes BC-93

North Dakota
US 83 becomes MB-83
ND-32 becomes MB-32
US 75 becomes MB-75

Minnesota
US 59 becomes MB-59
MN-89 becomes MB-89
MN-61 becomes ON-61

This doesn't seem to happen further east though.

[corco]

I'd say that's a function of the eastern Canadian highway system developing well before the western Canada system did. BC actually underwent a whole renumbering at some point in the 50's (?) to align BC 99 to US 99, BC 97 to US 97, BC 22 to what used to be Wash. SH 22, and so on and so forth

[yanksfan6129]

In the east, it happens in Maine. Off the top of my head, I-95 becomes NB 95.

[un1]

US 61 used to touch the border, where it became ON-61. Then they changed it to MN-61.