What is the theme in Cannery Row by John Steinbeck?

Community is the major theme of the book. Cannery Row looks at select aspects of community life in the seaside section of Monterey, California, as it rides out the Depression. Financial drives for various charities abound, with Dora Flood, owner/operator of the Bear Flag brothel being squeezed to contribute more than anyone as a condition for the community tolerating her illegal operation. During the worst years of the Depression, Flood nearly bankrupts herself helping families survive, and during an outbreak of influenza, despite a particularly booming business, has her cook prepare cauldrons of soup for distribution to sick folk by her girls.