After Napoleon's defeat in 1815, the Vienna Congress took place, in which many European borders were re-defined. Because of the important zinc mine and industry near Kelmis, the Unified Kingdom of the Netherlands (later Netherlands and Belgium), and the Kingdom of Prussia (which later became part of Germany) could not agree on whom the area belonged to. Hence they agreed to create a neutral area, with both countries appointing a commissioner to promote their country's interest in the area. The borders of the respective countries ended on the northeast and southwest, requiring exiting either country before entering the neutral area.

Although never a real state, the territory had a great similarity to one, completely with its own set of laws: due to the disputed ownership of the area, the countries agreed to keep Napoleonic law in force in the territory, with -missing an own court- Prussian and Belgian courts to interpret and judge according to that law. Also the separate and advantageous tax regime helped creating a great level of independence of the neighbouring states.

The zinc industry was the most important income of the country, however other income such as cheap goods, liquor and gambling has been important in bigger or smaller degrees over time.

With the Treaty of Versailles, the country became officially part of Belgium, thereby ending its century of independence. Nowadays it is part of the German speaking part of Belgium, placing it companionship with cities such as Eupen and St. Vith.

50.7088896.0433331 Hergenrath station sits in the east of the municipality, about 2.00 km (1.24 mi) east of the main town of Kelmis, being served by the EuregioAixpress (RE29) Liège - Verviers - Welkenraedt - Aachen.
50.659175.9752 Welkenraedt station is served by both RE29 and InterCity trains from Brussels, but more difficult to reach by bus from Kelmis. Taking IC 01 to Eupen, and then bus 396 is a better option.
Aachen, 8.00 km (4.97 mi) away across the border, sees German regional services, ICE and Eurostar service.

ASEAG bus route 24 from Aachen ends in Kelmis, running every 30 minutes except hourly on Sundays. German tickets are valid for the entire trip. Night bus service N7 runs on weekend nights.
TEC bus route 396 starts in the dutch town of Vaals, near the Dutch-German-Belgian tri point, passing through Kelmis and ending in Eupen, capital of the German Community of Belgium and terminus of IC 01 trains from Brussels. The route runs daily every hour, starting late in the morning on Sunday.
Bus 710 also links Welkenraedt and Kelmis, but takes a long route stopping in numerous villages like Henri-Chapelle, Montzen and Gemmenich, adding significant time to your journey.

European highway E40 passes nearby from Dunkerque, Ghent, Brussels and Liège, becoming Autobahn A44 across the border. Exit 39 Eynatten is the nearest exit, after a bit more than a kilometre turn left, from there it's still a couple of KM on Belgian country roads.
From Aachen proper you can also take highway B 264.