Fillmore Hatchery was one of the first warm-water hatcheries built in California to produce catchable-sized trout. Completed in 1942, the facility included 30 ponds, 4 cottages, a feed room, and a garage building, at a cost of about $74,000. In 1969, it was modernized as the dirt ponds were replaced with four 1,000-foot concrete raceways and a hatchery building with 7 circular tanks. As a major production hatchery, it raises about 252,000 pounds of rainbow, brown, and brook trout annually for Southern California anglers, including half a million rainbow trout stocked each year for recreational angling. From November through February, it partners with the Department of Water Resources to stock one-pound trout in Pyramid Lake for winter fishing. Its water comes from four large wells and ranges from 59 degrees in winter to 62 degrees in summer. Pumped from 150 to 600 feet below the surface, the water is cool and pure, and about 10.7 million gallons are pumped each day. After leaving the hatchery, the water is used by agriculture, then percolates back into sandy ground where filtration cleanses it for other uses.