SONOMA COUNTY -- The Lytton Band of Pomo Indians plans to deposit $10 million across four North Bay banks, part of an ongoing effort to broaden the tribe's business relationships in the region.

Tribal leaders signed off last week on the deposit of $2.5 million in interest-bearing accounts at AltaPacific Bank, Exchange Bank, First Community Bank, all based in Santa Rosa, and Novato's Bank of Marin, according to Larry Stidham, a long-time general counsel for the tribe and frequent spokesman.

"We wanted to look at ways of putting more money into local institutions," said Mr. Stidham. "We want to let the local banking community know we're here."

While noting that the deposit represented a relatively small proportion of the tribe's financial assets, Mr. Stidham said the move represented a tangible step in deepening ties to the North Bay business community. Lytton Rancheria has historic ties in Healdsburg and has spent $60 million--$70 million to purchase hundreds of acres of vineyards and other property in Sonoma County in recent years, he said.

The tribe owns and operates the San Pablo Lytton Casino in the East Bay city of San Pablo. Yet many members remain in Sonoma County, promoting interest in new ventures in the region, he said.

In late 2013 Santa Rosa City Council authorized the investment of up to $250,000 of city funds in any Sonoma County-based institutions with a satisfactory rate of return on interest-bearing deposits. Mr. Stidham said the move helped inspire the Lytton decision, though the tribe's deposit is significantly larger per institution and over a broader geography.

The tribe owns 350 acres of vineyards in Sonoma County, including the former Jordan Vineyards in the Alexander Valley, and sells its grapes in bulk, Mr. Stidham said. The Lytton Rancheria is also exploring new commercial investments throughout the region, though possibilities remain preliminary.

"What's important to us is economic diversification," Mr. Stidham said.

Lytton Rancheria is a major donor to Wells Fargo Center for the Arts, with recent donations that include funding for a half-million-dollar lobby renovation, he said.

"The Pomo people were here before anybody else," Mr. Stidham said. "They want people to know they're part of the community."