Hennepin County will be looking for a new library director now that Amy Ryan is headed to Boston.

Boston Public Library trustees Friday announced Ryan's appointment as president of the nation's oldest public big-city library system.

She's the first woman to head the 160-year-old system, a gender barrier that Hennepin County libraries broke back in the 1920s.

"It's a rare opportunity for a librarian to lead the Boston Public Library," said Ryan, whose parents are from suburban Boston. "I think that it was a good match for my experience and knowledge."

Ryan's decision to leave comes nearly eight months after Hennepin County and Minneapolis merged into a 41-library system. There is still substantial work to do to integrate the systems.

But she said she thinks employees are considering it one system.

"It's a loss for us," said Commissioner Gail Dorfman. "She was instrumental in getting us through the merger process. ... I wish she had been in a position to stay longer."

Ryan will be hard to replace because she has a rare combination of high-level administrative experience in both the city and county systems, said Jan Feye-Stukas, a library consultant who worked with Ryan in Minneapolis.

Although the position is considered attractive, the work remaining to fully blend the two systems could dampen interest, she said.

So could the pay. Ryan was paid more than $134,000 annually. Her predecessor in Boston was paid $167,000. Orange County, Fla., with a population similar to Hennepin County, paid $163,000 last year.

The person who replaces Ryan will be only the seventh person to lead county libraries in their more than 80 years.

Robert Rohlf, who headed county libraries for 25 years, said he wouldn't be surprised to see commissioners turn to Kit Hadley. She headed Minneapolis libraries until the merger and now is a consultant.

But there are three potential problems. First, the law requires the library director to hold a graduate library degree, which Hadley lacks. She took the Minneapolis position only after the City Council waived a similar requirement.

Second, there could be hard feelings left from last year's attempt by County Administrator Richard Johnson to appoint her his deputy. Enough commissioners objected to putting Hadley in a position supervising Ryan that she withdrew.

Third, some commissioners were harshly critical when the cost of merging the libraries turned out to be more than expected. It's open to speculation whether any of that would spatter on Hadley, who couldn't be reached Friday.

The new director by law will be appointed by Johnson, subject to board approval. The county's advisory library board must make recommendations.

Ryan's strong background in working with Minneapolis neighborhoods on branch libraries was considered to be a plus in Boston. "I cut my teeth on neighborhoods in Minneapolis," said Ryan, 57.

But Boston will be a different political environment. "All I can say is it's not Minnesota Nice in Boston," said Dorfman, who worked there years ago. "It'll be a significant change for her in politics."

Ryan's predecessor was forced out in a clash with Mayor Thomas Menino.

Steve Brandt • 612-673-4438