Pierson B. Reading Names the Trinity River in 1847

The Trinity River was known to trappers of the Hudson’s Bay Company as they passed through Northern California, but these early explorers apparently never gave it a name.
It was christened in May 1847 by Major Pierson B. Reading, referring to old Spanish charts that erroneously showed the river leading to Trinidad Bay, present-day Humboldt Bay, on the Northern California Coast.
Reading’s error led to excitement and confusion as anxious miners tried to reach the gold mines from the coast.  Most of them believed that by reaching Trinidad Bay they could continue upriver by boats to the mines.  Many who came in boats from San Francisco to head up the Trinity found themselves on the Eel or the Klamath River, and some on the Klamath thought they were on the Rogue.
The question of how best to reach the interior mines was resolved by prospecting parties traveling inland from Sacramento.
The Trinity is a major tributary of California's Klamath River.  The Trinity flows through wilderness before reaching the Klamath, attracting present-day salmon and steelhead fishermen, rafters, kayakers and canoeists.
 
Source: “Trinity River: The River Kept Its Secret." Trinity, 1955, pp. 33-35.