Starting in 1860, a number of small businesses and cottage workshops began manufacturing watch and clock parts. The Olten-Biel railroad built a station in the village in 1857. Around 1900 a watch factory and a brick works opened in the village. By 1904 the watch factory employed 80 workers. The factories, good roads and railroad connections transformed Pieterlen from a farming village, producing grain and wine, into an industrial town. The rapidly growing population required places to live so the workers' settlement of Sonnenhof and the new neighborhoods of Rebenweg, Romontweg, Rain and Löschgatter were built to house them. After the departure of the watch industry in the 1970s and 1980s, the town diversified its industrial base and built the Industrie-West industrial zone. In 2005 nearly half (49%) of the working population work in industry, while 47% work in the services sector. Starting in 2002, a section of the A5 motorway from Solothurn to Biel was built through the municipality.