Michael J. Jones will become president and chief executive officer of the Institution for Savings effective July 1.

Jones succeeds Mark F. Welch will retire tomorrow after a 35-year career at the Institution for Savings.

Jones, 42, is one of the youngest presidents in the bank’s history as well as that of a billion dollar Massachusetts-based bank, according to a statement.

Kimberly A. Rock will succeed Jones as the bank’s executive vice president and chief operating officer. Currently the bank’s senior vice president of retail banking, Rock, 44, has spent her entire professional career at the Institution for Savings, rising up through the ranks from teller to her current position where she oversees the bank’s extensive retail operations.

"As a Newburyport resident in the 1990s I chose the Institution for Savings as my personal bank and often told people that I would one day work there. I never realized that it would be as its president and CEO," said Jones. "My intent as president will be to improve upon that distinction by enhancing the bank’s competitiveness, expanding its market share and increasing our capital and total assets."

Jones and Welch together initiated and implemented the 2007 merger of the Institution for Savings with the Ipswich Co-operative Bank. The union resulted in combined total assets of nearly $800 million, which have grown to more than $1 billion as of the first quarter of 2010, according to a statement.

In late 2007, the bank opened a new office in Rowley, bringing to six the number of total offices in Newburyport, Salisbury, Rowley and Ipswich.