California designated redwood as the official state tree in 1937 (the coast redwood: Sequoia sempervirens, and the giant sequoia: Sequoia gigantea).

The giant sequoia is the most massive tree in the world, with 30- foot diameter trunks not uncommon. They reach ages of over 3,000 years. The coast redwood is the tallest tree in the world, averaging about 300 feet high. The oldest known redwood trees lived to be 2,200 years old.

In the mid - 1700's coast redwoods covered nearly 2 million acres. Since then 96 percent of that magnificent forest has been harvested - just 4 percent remains today for us to protect.

Source:

Among the Giants by Bob Neubauer
California Redwood: California State History Museum
The Brotherhood Tree: Trees of Mystery

Links:

Redwood National and State Parks: National Park Service
Redwood National Park: California Guide
Sequoia National Park: California Guide
Redwood Chapter: Sierra Club
State Trees - 50 States List