The company agreed to buy Charter Bank, which has four branches and $161 million in assets.
American Bank & Trust opened after organizers raised more than $22.5 million.
Blue Ridge Bankshares will be based in Charlottesville, Va., after completing its $43 million purchase of Virginia Community Bancshares.
Heritage will have 17 branches around San Francisco when it completes the $200 million acquisition.
The new capital will allow the Austin bank to increase its lending limit.
The company said it could use proceeds from selling common and preferred stock to increase lending and add branches.
The coastal city quickly rebounded after being hit by Hurricane Harvey in August 2017.
The proposed merger will create a bank with more than $1 billion in assets.
Triad Business Bank adds to the list of de novo efforts taking place in the state.
Sound Bank has new management as part of the transaction. It will also get a new name and expand into higher-growth markets.
