Humboldt Bay is the only deep water bay between the San Francisco Bay and Coos Bay, Oregon.
The Port of Humboldt Bay is the only protected deep water port for large ocean-going vessels for the large region.
Despite being the only protected harbor along nearly 500 miles (800 km) of coastline, the bay's location was undiscovered or at least unreliably charted for centuries after the first arrival of European explorers to the Pacific Coast.
This is partially because the bay is difficult to see from the ocean.
The harbor opens to the sea through a narrow and historically treacherous passage, which was blocked from direct view because of sandbars.
Formation of such sandbars is now managed by a system of jetties.
Contributing to the bay's isolation were features of the coastal mountain range, which extends from the ocean approximately 150 miles (240 km) inland, and the common marine layer (fog) in addition to frequent clouds or rain.

The bay is approximately 14 miles (23 km) long but can be from 0.5 miles (0.80 km) wide at the entrance to the widest point at 4.3 miles (6.9 km) in the North Bay.
 The surface area of Humboldt Bay is 16,000 acres (65 km²) of which 6,000 acres (24 km²) are intertidal mudflats.
More than 5,000 acres (20 km²) are primarily eelgrass habitat, which has been relatively constant since 1871, although more than 80% of the bay's coastal marsh habitats have been lost or fragmented by levee, railroad and highway construction.
At high tide the surface area is approximately 24 square miles (62 km²), but it is 10.8 square miles (28 km²) at low tide.
Each tidal cycle replaces 41% of the water in Humboldt Bay, although exchange in small channels and sloughs of the bay can take up to three weeks.
Humboldt Bay is the only deep water bay between the San Francisco Bay and Coos Bay, Oregon. The Port of Humboldt Bay is the only protected deep water port for large ocean-going vessels for the large region. Despite being the only protected harbor along nearly 500 miles (800 km) of coastline, the bay's location was undiscovered or at least unreliably charted for centuries after the first arrival of European explorers to the Pacific Coast. This is partially because the bay is difficult to see from the ocean. The harbor opens to the sea through a narrow and historically treacherous passage, which was blocked from direct view because of sandbars. Formation of such sandbars is now managed by a system of jetties. Contributing to the bay's isolation were features of the coastal mountain range, which extends from the ocean approximately 150 miles (240 km) inland, and the common marine layer (fog) in addition to frequent clouds or rain.
The bay is approximately 14 miles (23 km) long but can be from 0.5 miles (0.80 km) wide at the entrance to the widest point at 4.3 miles (6.9 km) in the North Bay.  The surface area of Humboldt Bay is 16,000 acres (65 km²) of which 6,000 acres (24 km²) are intertidal mudflats. More than 5,000 acres (20 km²) are primarily eelgrass habitat, which has been relatively constant since 1871, although more than 80% of the bay's coastal marsh habitats have been lost or fragmented by levee, railroad and highway construction. At high tide the surface area is approximately 24 square miles (62 km²), but it is 10.8 square miles (28 km²) at low tide. Each tidal cycle replaces 41% of the water in Humboldt Bay, although exchange in small channels and sloughs of the bay can take up to three weeks.
Humboldt Bay