The Carrizo Plain is a large enclosed grassland plain in southeastern San Luis Obispo County, California. It is the largest single native grassland remaining in California and it contains Carrizo Plain National Monument (246,812 acres or 99,881 ha). In 2012, it was further designated a National Historic Landmark due to its archeological value. The San Andreas Fault runs across the plain.

Wikipedia

The large basin of Soda Lake is all that remains of a prehistoric sea. One of the largest undisturbed alkali wetlands in the state, the 3,000 acre-lake provides important habitat for migratory birds. With no outlet, the water evaporates, leaving behind a glistening expanse of sodium sulfate and carbonate salts that appear to ripple and sway in the heat waves of summer.

In the 1880s, the saline deposits of Soda Lake were mined for use at nearby cattle ranches as salt licks or for preserving meat. Prior to 1908, the Carrisa Chemical Company constructed a 600 ton per month capacity-processing plant to recover sodium sulfate, used primarily in the production of craft paper, detergents, and glass. They also built a narrow-gauge railroad which started at the lake and ended at the base of the Temblor Mountains. Mineral production ceased in the 1950s, and the railroad was removed.

The monument description

Much of the area around Soda Lake contains spiny saltbush and open flat areas of alkali-based soils. The area can be alive with wild flowers in response to a wet year. Larkspur can be found among the saltbush, along with splashes of goldfields and smaller numbers of Munz's tidy-tip. Purple owl's clover can be found mixed with goldfields. In the bottom of the alkali sink area will be found the lemon yellow flowers of Jared's pepper-grass, along with red-stemmed filaree.

The monument description (edited)