Happy birthday, El Madrigal! The ground was opened on this day 90 years ago, with a match between Castellon and Cervantes (remember, Villarreal's club had just been founded, so maybe they weren't ready yet). It was first called "Campo del Villarreal" (Villarreal Field) but renamed a couple of years later.
There is a short history with photos of the stadium here:
and a couple of photos from the air at this site:
As Chris Clements notes, the first ground was basically a fenced-off field with a bit of terracing, and the earliest photo he could find is form the 1950s. What we see now was built once Sr. Roig arrived in the late 1990's, plus major renovations took place in order for Villarreal to host Champions League matches.
The stadium--or at least the offices--are going to be busy today, as season ticket sales have started. Current subscribers only at this point, but beginning June 26 new subscribers may sign up.
The goal of 20,000 tickets is nothing but not ambitious, but with incredible deals on season tickets (the lowest prices in La Liga) and the atmosphere around and inside the ground the last month or so, I expect we will get there! Endavant!