Daniel J. Callahan III, who resigned last week as chairman of Riggs National Corp., yesterday was named vice chairman of American Security Bank, the District's second largest bank and Riggs' chief competitor.

Callahan, 50, will be in charge of metropolitan, national and international commercial banking in a new senior management organizational structure announced yesterday by W. Jarvis Moody, chairman and chief executive officer of American Security Corp. and its subsidiary bank.

In other changes announced by Moody, James F. Rogers, executive vice president of both the bank and parent corporation, has been named president of American Security Corp., and Douglas T. Ledwith has been promoted to executive vice president. Ledwith had been chief financial officer.

The appointments will become effective April 19 when American Security's board holds its organizational meetings.

Callahan abruptly terminated a 10-year tenure at Riggs, including seven years as president, by submitting his resignation as chairman of the holding company. His resignation is one of several that have come in the wake of a management shakeup initiated earlier this year by Riggs Chairman Joe L. Allbritton who bought control of the $3.7-billion-asset institution two years ago.

Allbritton took full control of the bank in January when he replaced former chairman Vincent C. Burke Jr. as chief executive officer and wrested operating control from Callahan, who continued as president of Riggs National Corp.

Callahan's resignation surprised few in the local banking industry, because he was left with virtually no power after Allbritton took over as chief executive officer of the corporation and its only subsidiary.

With the appointment of Callahan and other senior executives named yesterday, American Security "will have created one of the strongest, most versatile management teams in American banking," Moody said.

In addition to being president and chief operating officer of the parent corporation, Rogers, who most recently had been executive vice president of both companies, will continue to be in charge of corporate administration of the bank.

John E. Sumter Jr. will continue as vice chairman in charge of major corporate accounts, and Kevin G. Woelflein continues as bank president and chief operating officer, with primary responsibility for credit, operations, audit and control.