All of west Netherlands except rivers and a few dunes is below sea level, separated by dikes into about 3000 independent hydrological units. These polders, their systems, and a culture evolved as the ground subsided. Delta peat bog, this land has degraded with settlement and agriculture.
There had been polders along the coastline, releasing water at low tide. But the great majority of polders formed and the techniques evolved in the settlement and tillage of inland farms where drainage to outside water had become increasingly problematic.
Though a polder is below water table, most began as farms on elevated bog. This ground, barely soil at all, required extensive work just to render it arable. The most destructive process, which continues today, was drainage. Without protection of stagnant water, peat is exposed to oxygen, and it decomposes.
So most polders formed not by "reclamation" (a misnomer -- landwinning, in Dutch) but by infrastructural response to subsiding land.
During the 17th century, there came projects that indeed made land of watery territory. By the time of the Golden Age, there were powerful standard-model water windmills, and the enormous wealth of the era permitted their deployment in huge numbers.
In 1612 the Beemster, a lake formed by peat harvest and widened by stormflood erosion into a problematic arm of the Zuiderzee, had been bedijked and pumped by the use of windmills. Following the technical (eventual) success and enormous profitability of the entrepreneurial drainage and division of the Beemster into farmland parcels, the rest of the delta's shallow lakes were dried within the next few decades. Political will was easy because the lakes were a stormflood hazard and an erosion menace and there was plenty of capital for good lakebed farmland. The windmills had created and maintained a couple hundred square kilometers of terrain.
It wasn't until 1811 that anybody would initiate another major *landwinning* project, the Zuidplaspolder in South Holland province. Centuries of peat harvest had led to lake Zuidplas, and it was a menace to bordering properties. Also, the 19th century brought again a high demand for arable property. Gangs of windmills emptied Zuidplas, tens of meters deep. A few decades later the Netherlands' first large steam pumping station assumed maintenance drainage.
The steam pump-station came into its historical moment in the early 19th century when the technology coincided with sufficient political will to drain the great Haarlemermeer, a menacing body of water in the south of North Holland province. Adjacent municipalities had since the Middle Ages harvested peat from the deepening beds of lakes that had eroded into one lake that ate villages during stormy weather. three steam pumping stations drained Haarlemermeer between 1848 and 1852.
In 1891 the engineer Cornelius Lely drafted a plan for closing the Zuiderzee, a great shallow inland sea extending into the heart of the Netherlands. There was opposition , but Zuiderzee was problematic in proportion to it size. After the 1916 flood, Plan Lely became reality. A 1918 law decreed the closure and impoldering of the Zuiderzee. The first world war delayed execution of Lely's plan, but also showed the food security importance of a greater expanse of farmland.
An experimental polder completed in 1927 showed the arability of the dried seabed. In the next few decades Plan-Lely claimed more than 1700 square kilometers by the use of large electric pumping stations. Much of the former Zuiderzee (now the freshwater lake Ijselmeer) is now farmland. Part of that is the twelfth province.