Definition of "border"

The identification of the border between England and Scotland always has been a source of interest to railway travellers. For many years, however, the exact points north of Berwick and Carlisle at which the Anglo-Scottish main lines passed from one country to the other were not defined, but the erection of clear and unmistakable lineside signs has put the matter beyond all doubt.

1950 January, “Crossing the Border”, in Railway Magazine, page 2

The Ministry of Defence said on Wednesday the men had been killed on Tuesday in the Nahr-e Saraj district of Helmand province, on the border of Kandahar just north of the provincial capital Lashkar Gah.

2013, Nicholas Watt and Nick Hopkins, Afghanistan bomb: UK to 'look carefully' at use of vehicles(in The Guardian, 1 May 2013)

A French tourist who accidentally crossed the border into the US from Canada during an evening jog was sent to a detention centre 125 miles away and held for two weeks until she was released.

23 June 2018, Mattha Busb, The Independent, Jogger crosses US-Canada border by mistake, is held for two weeks in detention centre

upon the borders of these solitudes

1843, Jeremy Bentham, Principles of Morals and Legislation, Fragment on Government, Civil Code, Penal Law

in the borders of death

a. 1678 (date written), Isaac Barrow, “(please specify the chapter name or sermon number). The Danger and Mischief of Delaying Reptentance”, in The Works of Dr. Isaac Barrow. […], volumes (please specify |volume=I to VII), London: A[braham] J[ohn] Valpy, […], published 1830–1831

Wit which borders upon profaneness […] deserves to be branded as folly.

1671, John Tillotson, “Sermon II. The Folly of Scoffing at Religion. 2 Pet, published 1720