The site of La Chaux-de-Fonds / Le Locle watchmaking town-planning consists of two towns situated close to one another in a remote environment in the Swiss Jura mountains, on land ill-suited to farming. Their planning and buildings reflect watchmakers’ need of rational organization. Planned in the early 19th century, after extensive fires, the towns owed their existence to this single industry. Their layout along an open-ended scheme of parallel strips on which residential housing and workshops are intermingled reflects the needs of the local watchmaking culture that dates to the 17th century and is still alive today. The site presents outstanding examples of mono-industrial manufacturing-towns which are well preserved and still active. The urban planning of both towns has accommodated the transition from the artisanal production of a cottage industry to the more concentrated factory production of the late 19th and 20th centuries. The town of La Chaux-de-Fonds was described by Karl Marx as a “huge factory-town” in Das Kapital where he analyzed the division of labour in the watchmaking industry of the Jura.