Delaware,
Pennsylvania
Pennsylvania shares the longest border.
New York
Pennsylvania borders Maryland to the south.
North Dakota and Idaho share a land border with Canada. Pennsylvania shares a maritime border with Canada across Lake Erie.
Vermont shares its northern border with New York.
Delaware shares a border with Pennsylvania and with Maryland.
Maine, it shares a border with Vermont.
The state that shares its northern border with Connecticut is Massachusetts.
There is no Australian state which shares a border with all other states. No state except for Victoria shares a land border with Tasmania. South Australia shares a border with all mainland states and the Northern Territory.
Oklahoma shares most of Texas's northern border.
South Dakota shares its northern border with Nebraska.