The city is closing Camp LaGuardia, its largest homeless shelter for single adults and the only one outside the five boroughs.

Saying the city’s shelter population has dropped so much that there was no longer a need for the facility, officials hailed the move as a sign that the Bloomberg administration’s efforts to reduce homelessness are working. First opened in Orange County as a shelter for adult men in 1934, Camp LaGuardia currently houses 700 residents but will be empty by June.

The city sold the site to the county for $8.5 million, and it will reinvest the $19 million budgeted for its use into programs to prevent homelessness, officials said.

The shelter’s closing has been a long time coming for advocates of the homeless, who decried its “warehouse”-style conditions, and for residents of Orange County, who did not want a homeless shelter in their community. It also saves money for the city, which spent millions of dollars transporting homeless New Yorkers 60 miles by bus every day.

“It’s been a thorn in everybody’s side for a long time,” Mayor Bloomberg said yesterday.

The mayor has set a goal of reducing the city’s homeless population by two-thirds by the time he leaves office. The number of single adults sleeping in city shelters has dropped by more than 1,000, or 13%, in the last two years, the city says. About 7,400 single adults slept in city shelters Wednesday night, according to data from the Department of Homeless Services.

While the homeless population of single adults in shelters has dropped, homeless families are on the rise, city statistics show. In a statement issued yesterday, the executive director of the Coalition for the Homeless, Mary Brosnahan Sullivan, applauded the closing of Camp LaGuardia as “welcome news,” but she added: “At the same time we remain extremely concerned that the family shelter population continues to increase at a rapid pace.”

More than 9,000 families slept in shelters Wednesday night, an increase of more than 1,100 from a year ago.

Mr. Bloomberg acknowledged that the city was ‘slightly behind” its goal for homeless families, but he said he was optimistic that it would be reached by the conclusion of his term at the end of 2009.

Built in 1918, the 300-acre Camp LaGuardia straddles the towns of Chester and Blooming Grove. The city took it over in 1934, after it had served as a women’s jail for 16 years. Of the 700 people living in the camp, one-third are expected to be placed in supportive housing by the time the facility is transferred to Orange County in June, one-third will be moved to other shelters, and one-third are expected to leave the system voluntarily. Beginning yesterday, no one else will be referred to the camp.