The area became Prussian in 1815. To help govern its new land Prussia made three districts Heinsberg, Erkelenz and Geilenkirchen in 1816. In 1932 the districts of Heinsberg and Geilenkirchen were joined, and in 1972 the Erkelenz district was joined to the others as well. In 1975 the municipality of Niederkrüchten was moved to the district Viersen. That was the last change to the district's size
The coat of arms show two lions in the top part, in the left the silver lion of the city and the dukes of Heinsberg, in the right the black lion on yellow ground of the duchy of Jülich. The bottom part is from the coat of arms of the old district of Erkelenz, the fleur-de-lis from the city of Erkelenz is for the Maria-abbey in Aachen, and the blue flax flower in the middle remembers the old industry of flax and linen trading in Erkelenz.