Island No. 1

1 (formerly called Cross Island)[2] is a partially submerged island in the Napa River, upstream of San Pablo Bay (an embayment of San Francisco Bay).

[3][4][2] It is in Napa and Solano County, California, and parts of it are managed as part of the Napa-Sonoma Marshes Wildlife Area.

1)[1], and the United States Geological Survey measured its elevation as 3 ft (0.91 m) in 1981.

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Island No. 1 as it appears on a 1951 USGS topographic map.
Aerial image of an island.
USGS aerial imagery of Island No. 1 in 2021.
An aerial view, looking toward the west, of the Napa River where it flows into San Pablo Bay through Vallejo . Islands visible include, from bottom of image: Mare , No. 1, Knight , Russ , No. 2 , Green , Bull , Edgerly , Coon , Little , and Tubbs .