By the 1890s, Hong Kong Island and southern Kowloon had been ceded to Britain outright — the permanent spoils of two opium wars. But the colony's security chiefs were nervous. The hills of Kowloon overlooked Victoria Harbour and Victoria City; any hostile force holding those heights could threaten the entire settlement. Bubonic plague had struck Hong Kong in 1894, straining resources. And across the region, European powers were carving up Chinese territory with alarming speed — France had established Guangzhouwan to the west, and Germany held Jiaozhou Bay to the north.

Britain responded by invoking the most-favoured-nation clause it had extracted from China years earlier. In June 1898, the UK demanded and received the New Territories as a leasehold from the Qing court. The additional land was estimated at twelve times the size of the existing colony. It was a pragmatic land grab dressed in the language of security and administration, and it would define Hong Kong's geography for more than a century.

The British assumed the handover would be orderly. It was not. The convention was signed on 9 June 1898, took effect on 1 July, but Britain did not actually move to occupy the New Territories until April 1899 — and when they did, the indigenous clans were ready to resist.

Fearing the loss of their traditional land rights, clans across the region mobilised militias that had long been used against coastal pirates. On 14 April 1899, the day designated for the formal flag-raising ceremony, militiamen attacked the temporary British post at Tai Po, burning the matshed the British had erected for the occasion. The assault was beaten back. A subsequent attempt at guerrilla warfare near Lam Tsuen ended with over 500 Chinese men killed when British artillery was brought to bear. The most prominent resisting village, Kat Hing Wai of the Tang clan, was symbolically disarmed — its main gates dismounted and removed.

To prevent further resistance, Britain made significant concessions on land use, land inheritance, and marriage laws. Most of those concessions remained in place into the 1960s. Some aspects of customary land law in the New Territories still differ from the rest of Hong Kong today, a source of continuing friction between indigenous inhabitants and other residents.

For the first half of the twentieth century, the New Territories stayed largely rural — a patchwork of rice paddies, fishing villages, and walled ancestral settlements separated by low mountains and tidal inlets. It was not until the late 1970s that large-scale urban development arrived, driven by the need to house a population that had been swelling since the refugee influxes of the 1940s and 1950s.

New towns — Sha Tin, Tuen Mun, Tai Po, Fanling, Yuen Long — were built from near scratch, eventually accommodating more than three million people. Yet the Hong Kong government deliberately confined development to a relatively small footprint. Around those new towns, large sections of the New Territories were protected as country parks. The result is a striking landscape of contrasts: tower blocks and expressways threading through valleys flanked by uninhabited ridgelines, where hikers can walk for hours without encountering a single road.

As the 1980s began, the expiry date of the 1898 lease started concentrating minds. The New Territories lease ran until 1 July 1997. Britain could theoretically have retained Hong Kong Island and southern Kowloon — both ceded outright, not leased — but in practice the three areas were so economically and administratively intertwined that separation was unworkable. Negotiations between London and Beijing led to the Sino-British Joint Declaration of 1984, committing the whole of Hong Kong, leased and ceded territories alike, to Chinese sovereignty on that same 1997 deadline.

On 1 July 1997, sovereignty transferred to the People's Republic of China. The New Territories, along with Hong Kong Island and Kowloon, became a Special Administrative Region. By the 2021 census, the New Territories held 3,984,077 people — 53.7 percent of Hong Kong's entire population — spread across nine districts covering 952 square kilometres. The land that Britain acquired to protect a small island colony had become home to more than half the people in one of Asia's great cities.