There are three primary subspecies of elk (also known as wapiti, scientific name Cervus canadensis) in the western US:
The Tule Elk were almost wiped out in CA by the early 1870s. They had been hunted nearly to extinction due to market hunting after the Gold Rush and habitat loss from agriculture and livestock grazing. They were thought to be gone by around 1870. Henry Miller (born Heinrich Alfred Kreiser), was a prominent German-American cattle baron and landowner in California's San Joaquin Valley and he is widely credited with starting the conservation of tule elk in the state.
In 1874, while draining a marsh on his vast Miller & Lux ranch near Bakersfield (in the Buena Vista Lake/Tulare Lake area), Miller's workers discovered a small remnant herd—estimates range from as few as 2–10 to about 30 animals.
Miller took decisive action. He immediately protected the elk on his property, banning hunting there. He sent vaqueros (cowboys) to search for any remaining animals. He ordered the herd to be safeguarded at all costs and kept its existence relatively quiet to avoid poachers (offering rewards for reports of threats).
By 1905, the protected herd had grown to around 140 animals. When the growing herd began damaging crops and fences, Miller captured some and moved them to other parts of California—the first deliberate conservation translocations of the subspecies.
Miller's efforts were among the first environmental programs in CA.
Today, the Tule Elk herds have grown and have been extended to many parts of the state. Pt. Reyes has a famous herd. There's a herd close to downtown San Jose. You can see Tule Elk in a fenced area at the San Luis National Wildlife Refuge in Los Banos. There's a five mile drive around the fenced-in area. It's a fun visit.

The Eastern elk (Cervus canadensis canadensis), a distinct population of North American elk that lived in the forests and woodlands from the northern and eastern U.S. to southern Canada. They are extinct.
The reintroduced herds in the East are Rocky Mountain Elk.
Henry Miller
That was the name of my grade school, 1st and 2nd grade, in Los Banos,,always wondered who he was and why a school was named after him.
Never knew about the reserve or elk.
Thanks for the backstory.