Richard Armstrong, the Henry J. Heinz II director of the Carnegie Museum of Art who has brought major renovations to the museum facilities and supported more expansive exhibitions, is leaving his position at the end of the year, Carnegie Museums of Pittsburgh announced yesterday.

Mr. Armstrong has been at the Carnegie since 1992, when he was appointed curator of contemporary art and charged with organizing the 1995 Carnegie International. He became chief curator later that year, and was appointed director in 1996.

Richard Armstrong

Reflecting on his decision, Mr. Armstrong, 59, noted it's atypical for anyone to stay in one job for 12 years.

"I looked at my game plan. I looked at the museum's game plan. It was a timely moment," he said.

He leaves the museum on solid ground, said museum board Chairman William E. Hunt.

"Physically and financially, it's in as good a shape as it has been in a very long time," Mr. Hunt said.

During Mr. Armstrong's tenure, the Heinz and Scaife galleries have been renovated, the Heinz Architectural Center expanded and significant support has been raised for endowment.

Among the latter are major gifts from the Fine Foundation in support of Carnegie International exhibitions, the Alan G. and Jane A. Lehman Foundation to establish a named curatorship in and acquisition of decorative arts, and the Jill and Peter Kraus Endowment for Contemporary Art.

Mr. Hunt, who has served eight years on the board, two of those as chairman, praised Mr. Armstrong as a wonderful director, articulate, with exceptional people skills.

Perhaps the most outstanding among his many accomplishments, Mr. Hunt said, is what Mr. Armstrong has done with his team.

"We have a world class group of curators," he said. "He's done a tremendous job with his management group as well as his educators. He has also made strategic and intelligent acquisitions."

When evaluating a museum director, what is brought into the collection during one's tenure is of upmost importance, and Mr. Armstrong gets high marks for how he's shaped and expanded the Carnegie's.

Numerous works from Carnegie International exhibitions have grown the contemporary holdings, in line with museum founder Andrew Carnegie's dictum to collect the "old masters of tomorrow."

Mr. Armstrong initiated the museum's first joint acquisition -- a practice gaining popularity among museums as the art market drives prices skyward and the sizes of contemporary works demand more floor space -- with the Albright-Knox Art Gallery, of Buffalo, N.Y., co-purchasing Rachel Whiteread's "Untitled (Domestic)."

Photography gained a strong presence through such additions as the archives of McKeesport native Duane Michals and of Charles "Teenie" Harris, whose work is considered to be among the most important documentations of African-American life in the 20th century.

"We've had a voracious appetite for acquisitions over the last 12 years," Mr. Armstrong said, purchasing, or receiving as gifts, 19th-, 20th- and 21st-century objects in every medium.

David Hillenbrand, president and chief executive officer of Carnegie Museums of Pittsburgh, said Mr. Armstrong will leave an "indelible mark" on the museum and on Pittsburgh.

"Richard's leadership has built a stronger museum -- one that is respected throughout this community for its great contributions to the Pittsburgh region's cultural and educational landscape," Mr. Hillenbrand said.

Mr. Armstrong, whose decision to leave is unrelated to yesterday's revelation of the defacing of a $1.2 million artwork beyond repair, is the third directorial loss Carnegie museums have suffered in recent years -- the head of the Carnegie Museum of Natural History left in 2007 and the head of the Carnegie Science Center resigned last month.

A native of Kansas City, Mo., Mr. Armstrong came to the Carnegie from the Whitney Museum of American Art in New York, and said he "fell in love with Pittsburgh and the people right then. I loved it from day one."

Marcia Gumberg, a Carnegie board member and former chairwoman, corroborates that.

"He shows great warmth to everyone and they love him back," she said. "We've had very good directors, but he is greatness personified."

Mr. Armstrong said that he has not yet committed to a new position and is planning to spend some time considering his "strategy for the next chapter" of his life, which may or may not include arts administration and will probably be in New York.

Mr. Hunt said that a search committee will be formed soon to look for a successor.

Mr. Armstrong began his association with the museum as a Carnegie International curator in the centennial year of the founding of that exhibition. He will leave the museum while its longest running International, "Life on Mars," is in full flower.