The town is a major railroad junction connecting the capital city of Warsaw with Gdańsk and Olsztyn to the north.

The new settlement near the castle founded by Mikołaj z Karbowa and named Soldov was granted town privileges on 14 August 1344 by the Grand Master Ludolf König.

The following communes belonged to the Protestant parish of Soldau: Amalienhof, Borowo, Bursch, Cämmersdorf, Gajowken, Hohendorf, Kyschienen, Königshagen, Kurkau, Niederhof, Pierlawken, Pruschinowo, and Rudolfsfelde.

Within the Kingdom of Prussia and the later German Empire, the settlement developed into an important Prussian Eastern Railway junction in the second half of the 19th century.

[6] At the same time the Prussian authorities were hostile to the local population due to its Polish pro-independence activity during the November and January Uprisings in Congress Poland.

During the January Uprising of 1863 an ammunition depot and contact point was secretly established by local people trying to help their fellow Poles in the struggle against the Russian Empire; it was located at the house of Doctor Russendorf.

During the German Nazi - Russian Soviet invasion of Poland in 1939 that began World War II, the town was invaded by Germany, and then the Einsatzgruppe V entered to commit crimes against the Polish population.

The German minority in the town formed the Selbstschutz death squad that captured and tortured Polish leaders and members of the political and cultural elites before murdering them.

[7] Only some of the local Polish activists were caught by the Germans, as most fled and hid under assumed names in the General Government (German-occupied central Poland).