<Tr> <Th> Treaties </Th> <Td> Anglo - Irish Treaty </Td> </Tr> <Tr> <Th> Notes </Th> <Td> Open border not officially marked by either government </Td> </Tr> <P> The Republic of Ireland--United Kingdom border runs for 499 km (310 mi) from Lough Foyle in the north of Ireland to Carlingford Lough in the northeast, separating the Republic of Ireland from Northern Ireland . </P> <P> Border markings are comparatively inconspicuous, in common with many international borders in the European Union . As both states share a Common Travel Area and are part of the European Single Market, the border is essentially open, allowing free passage of people since 1923 and of goods since 1993 . There are more than 200 public roads that cross the border . Following the Brexit vote, the future of the border is uncertain and its status is one of the key points in the UK withdrawal negotiations . </P>

Where is the border between north and south ireland
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