Between Canada and the US.
================================================================================
An open border is one that allows unrestricted entry and exit. The border between Canada and the US has been described as the world's longest "undefended" border, but it is not an "open" border. Even the "undefended" concept of the Canada-US border is now being questioned.
The Amazon River in South America is the longest river in the world. Tennessee does not border it.
worlds longest toenailes
The worlds longest road bridge is in China
California has the longest border with Nevada.
Kentucky has the longest border with Tennessee.
The longest border in Spain is the border with Portugal to the west. The border with Portugal runs from the north of Spain to the south.
India has the longest border with the Arabian Sea.
Brazil shares its longest border with Bolivia.
Libya has longest border on Mediterranean
At 8891 km, the border between Canada and the USA is the longest between any two countries, but a major section of that border (with Alaska) is not contiguous with the rest. The longest contiguous section of border between two countries in the world is between Russia and Kazakhstan, at 6846 km.
No, Ontario has the longest border with Canada and the US.
Pakistan has the longest border with Afghanistan. It stretches for over 1500km.