Before the causeway, getting to Sylt meant a paddlesteamer. The west coast railway ran north from Altona through Husum and Niebüll to Tondern, and from there tracks continued to the port at Hoyerschleuse, where boats crossed to Munkmarsch on Sylt. The service depended entirely on the tide, and in hard winters the ice in the Wadden Sea shut it down completely. Westerland had become a town in 1905 and was growing into a serious seaside resort, so by 1910 the authorities were planning a rail causeway in earnest. The war stopped everything. Then the peace made it urgent: under the postwar settlement, Tønder and Hoyerschleuse went to Denmark. Sylt stayed German, but the only practical route to it now ran through another country, and a short trip to the beach meant applying for a Danish visa.

Construction began in 1923 and ran for four years. Philipp Holzmann AG of Frankfurt worked outward from the mainland; Peter Fix Söhne of Duisburg worked back from Sylt. Early on, a storm surge simply erased what had been built, and the engineers responded by shifting the alignment further north and driving a trench-like cofferdam ahead of the works. Between 1,000 and 1,500 men were employed. They moved more than three million cubic metres of sand and Klei — the heavy grey clay of the tidal flats — and dumped 120,000 tonnes of stone to armour the flanks. On 1 June 1927 the causeway opened. Reichspräsident Paul von Hindenburg came for the ceremony and rode the first train across; at the breakfast afterwards, the railway official Julius Dorpmüller gave the structure his name.

The Hindenburgdamm carries the Marschbahn, the Marsh Railway, double-tracked for most of its length though single-tracked in places, with a signal box standing alone out on the causeway. The line is not electrified, so trains from Hamburg and further south swap their electric locomotive for a diesel at Itzehoe before continuing north. Two operators run the car shuttles: DB's Sylt Shuttle in red and RDC's Autozug Sylt in blue, both loading at Niebüll and unloading at Westerland thirty minutes later. Riding it is not scenic in the conventional sense. On one side and then the other there is water, or mud, or a sheet of something in between, depending on the hour — and then dune grass, and then Sylt.

Before 1927 the tide moved freely through the channel between Sylt and the mainland. The causeway put a wall across it, and the water has been rearranging itself ever since. The interruption to tidal flow is understood to be part of why Sylt keeps losing ground at its southern tip, at Hörnum Odde, where the shoreline has been in retreat for decades. The causeway itself now lies inside Zone I of the Schleswig-Holstein Wadden Sea National Park, the most strictly protected category, which is why the mudflat walks that are a regional institution everywhere else along this coast are forbidden here. Not everything about the crossing has been peaceful either: on 3 September 2009 a squall blew a truck off a flatcar mid-causeway, throwing the driver from the cab and killing him.

By the 1960s the name had become a problem. Hindenburg was the Reichspräsident who appointed Hitler chancellor, and Germany spent the postwar decades reconsidering what it wanted written on its infrastructure. Alternatives were proposed and argued over — Sylt-Damm, Friedens-Damm for peace, Friesen-Damm for the Frisians whose coast this is — and none of them ever gathered a majority. Deutsche Bahn has since floated Syltdamm again. The debate has now outlasted several generations of locomotive, which may be the most German outcome available. In the meantime the trains keep running, roughly every hour, plus the shuttles, plus the intercity services, and nearly a century of cars have crossed the Wadden Sea sitting perfectly still.