Officials of Contra Costa County, one of the wealthiest in the state, are trying to persuade their affluent cities to contribute funds for temporary homeless shelters. The officials are also fighting to keep National Guard armories open until they can find temporary shelter for more than 650 people who live on the county’s streets. “We didn’t have this uncaring attitude during the Depression,” said Larry Organ, an aide to county Supervisor Tom Powers. “People brought people in need into their homes. Now they wander the street while we’re in the most expansive economic period in our history since World War II.” Powers and Richmond Mayor George Livingston led a rally at a local armory to convince the governor and county residents that homelessness is everyone’s problem.