The Markerwaard is the name of a polder in the IJsselmeer that was never built. The construction of Markerwaard would have resulted in the near-total reclamation of the Markermeer.
Cornelis Lely's plan projected a polder in the south-west of the Zuiderzee, originally named simply "Southwest Polder". Later the name was changed to Markerwaard Polder, after the island of Marken. The Markerwaard would have had an area of 410 km². However, reclamation of three other polders took place first, and preparations for the Markerwaard were being made while draining of the northeast and southeast polders (today's Flevoland) were underway. In 1957, the island of Marken was connected to continental Holland. In 1976 the dam Houtribdijk connecting Enkhuizen and Lelystad was completed, a necessary step in the construction of Markerwaard. However, the draining made possible by the completion of the of the Houtribdijk was never started, as the entire project became mired in political and environmental controversy. In the 1980s, the project was revised down leaving bordering lakes between the polder and North Holland. Marken would remain a peninsula, unlike on the original project.
The debate on a final decision regarding Markerwaard took over twenty years. The questions concerned the need, on one side, for more agricultural areas, new residential subdivisions, and a new airport (to relieve pressure on Schiphol). On the other side of the debate were primarily ecological issues, with the argument that the value of the lake as a recreation area was considered by some to be stronger than the potential benefits of the polder. Additionally, it was argued that, in case of drought, the lake would be very useful for the production of drinking water, and that in heavy weather, the lake serves as a buffer zone.
Finally, in 2003, it was decided not to build this polder.
Interestingly, in 1941 the first dam for this project was built, but the German occupation stopped the work. Later, it was decided that Flevoland should have priority. Without this decision it is likely that the Markerwaard today would exist.