Doh, that was an easy one. According to NY Times (interesting article):

The first big bank collapse after the Crash of 1929 began at a little limestone branch built in 1921 at the southeast corner of Freeman Street and Southern Boulevard in the Morrisania section of the Bronx. Now little more than a shell, it is a ruined monument in the history of American finance.

The modest structure was the first Bronx branch of the grandly titled Bank of the United States, begun in 1913 by Joseph S. Marcus, a Lower East Side garment manufacturer and financier. It served both established and newly arrived immigrants and its ambitious name was apparently chosen to impress (or confuse). It had no Government connection and in 1926 such an appellation was outlawed, but the legislation was not retroactive.

The Bronx branch was built in 1921. A tiny little neo-classical limestone structure with a chamfered corner and great bronze torchieres outside, it was designed by Louis Allen Abramson.

Marcus died in 1927 and his son Bernard took over during the bank's expansion through mergers from five branches in 1925 to 62 throughout New York City in 1930.

The bank's stock was publicly traded and there were rumors in the financial community in mid-1929 that the institution was shaky, but it weathered the October 1929 stock market disaster. However, either continuing reports of its shaky finances or just depositors' needs for cash as the Depression began dropped its reserves from over $200 million in October 1930 to $160 million in December. And on Dec. 8 a previously announced merger with three other banks was called off.

On Dec. 10, a Wednesday, $2 million was withdrawn from the Bronx branch by 2,500 depositors, one of whom stood in line for two hours to empty a $2 savings account. The commotion attracted a crowd of over 20,000.

The next day, The New York Times attributed the rush to a "false rumor" by a disgruntled investor. Nevertheless, nervous depositors formed long lines at other branches. An unidentified bank officer contended that the trouble was started by brokers seeking commissions from panic selling of the bank's stock. But on Dec. 11, Joseph A. Broderick, New York State Superintendent of Banks, closed the institution. It never reopened.

The bank had 400,000 depositors -- more than any other in the country -- and immediately hurt were garment businesses that needed money for their payrolls. Claims began to be processed in an orderly manner, but on Dec. 21 a crowd of 3,000 shouting "We want our money!" tried to storm the padlocked Bronx branch. Six people were arrested, all Bronx residents. Charges were dropped the next day.

"A Monetary History of the United States" by Milton Friedman and Anna Jacobson Schwartz, calls its failure the largest ever in American banking up to that time. The bank ultimately paid out over 80 percent on its deposits. But the obvious public panic set the stage for a series of bank failures that continued until 1933. . . .