When the founding of the village had finally taken place, it still didn't have an official name, even though the locals called it Buitensluis.

But Dijkgraaf Vos, the chairman of the meeting, believed the village should me named after the first Ambachtsheer, Gerard Numan.

The first buildings of the village were built around the drainage sluice at the Numanspolderdijk (now called Molendijk) and from there the town spread along the Binnenhaven.

On 12 May 1940 the soldiers of the fort received the command to go to Westmaas where they were to secure the Barendrechtse brug (Bridge of Barendrecht).

In September 1944 the Germans moved the people of Numansdorp, because they wanted to flood the area as a defence against the Allies.

In the night of 31 January and morning of 1 February 1953 large parts of Zeeland, the islands of South Holland and some parts of North Brabant were flooded, due to a combination of high tide and a strong northwestern storm which caused many dikes to break.

A result of the flood was the death of 56 inhabitants of the area, which made the Numansdorp the village with the highest number on the Hoeksche Waard.

Because the fields had been flooded with salt water for 14 days, they couldn't be properly used for the rest of the year.