The reason anyone settled here at all is the Cửa Lớn, and it is a genuine oddity. Fifty-eight kilometres long, it is the only river in Vietnam that begins at the sea and ends at the sea. It has no headwaters and no lower course. Water enters at the Bồ Đề mouth on the South China Sea side, where the channel runs six hundred metres wide and nineteen metres deep, narrows to three hundred metres and fourteen metres of depth as it passes Năm Căn township, then fans out at the Ông Trang mouth on the Gulf of Thailand side into something closer to a bay — more than eighteen hundred metres across, but shallowed to four or five metres. What it really is, is a tidal channel connecting two seas that keep different schedules, and the South China Sea usually wins the argument. Distributaries branch off it every kilometre or less, some no wider than a ditch, others full rivers wandering off into the forest.

The Cửa Lớn does something else worth noticing on a map. Together with its associated channels it cuts the whole southern tip of the Cà Mau peninsula clean away from the rest of Vietnam — the cape, the national park, Rạch Gốc, all of it sitting on what is functionally an island, reached by the Năm Căn bridge. That crossing is why the town matters far beyond its size. Everything travelling by road to the southernmost point in the country passes through here, and Năm Căn port sits on the left bank just outside the settlement, working the estuary traffic in both directions.

The water here is neither salt nor fresh. A handful of small rivers — the Đầm Dơi, the Đầm Chim, the Cái Ngang — push freshwater in against the tide, and the brackish result is unusually productive. Năm Căn crab has a reputation across the delta, and the district's economy has always rested on fisheries first, with commerce and services layered on top: ice and fuel and chandlery for the boats, transport, hotels and restaurants, an industrial zone, and more recently ecotourism aimed at visitors heading for the cape. Kinh, Hoa and Khmer families cleared and settled these mangroves alongside one another, and all three communities still live here. The older trade of the district — cutting mangrove for charcoal — has largely given way to shrimp ponds, which is a mixed blessing for a coastline that depends on its trees.

Administratively, Năm Căn has led a restless life. In December 1984 the district was renamed Ngọc Hiển, after the executed revolutionary Phan Ngọc Hiển, and the old name disappeared from the register. It came back on 17 November 2003, when a decree carved a new Năm Căn district out of part of Ngọc Hiển. In its final form the district ran to 490.70 square kilometres across one township and seven communes — Hàm Rồng, Đất Mới, Hàng Vịnh, Hiệp Tùng, Tam Giang, Tam Giang Đông and Lâm Hải — with Năm Căn township as its seat. The 2019 census counted 56,813 people. By the end of 2024 the provincial figure had reached 81,095, most of the growth clustered around the port and the highway.

Then it vanished again, and this time not alone. On 12 June 2025 the National Assembly merged the neighbouring province of Bạc Liêu into Cà Mau; four days later it resolved to end district-level government throughout Vietnam, with effect from 1 July 2025. Every district in the country was dissolved at once, leaving provinces dealing directly with communes. What had been Năm Căn district is now covered by Năm Căn and Tam Giang communes and part of Đất Mới. None of which troubles the place much. The bridge still carries the road south, the port still works the tide, and the crabs are still sold under the name of five houses that a trader put up on the mud before anyone thought to write any of it down.