One of Wall Street's top bond-rating agencies, Moody's Investors Service, has given Loudoun County its highest rating, a distinction shared by just 42 counties nationwide that could save taxpayers millions in debt payments.

Moody's said Loudoun, the nation's fastest-growing county, had proven adept at managing the fiscal strains of booming home building, a conclusion that runs contrary to much of the high-decibel political rhetoric in the county. Politicians have long cited concerns about Loudoun's overall fiscal health to buttress their arguments for -- and against -- efforts to curb residential development.

Slow-growth advocates said that the high cost of schools and other projects associated with breakneck home construction threatened to drown the county in red ink. Meanwhile, development backers, including members of the Republican majority on Loudoun's Board of Supervisors, said wasteful spending and mismanagement by slow-growth advocates on the previous board endangered the county's fiscal future.

But the portrait of Loudoun offered by Moody's is one of overall economic health.

"Assignment of Moody's highest rating reflects the county's strong, diverse and growing tax base; high wealth levels; consistently solid financial performance; moderate but increasing debt levels; and Moody's expectations that these factors will remain favorable," according to the Moody's report.

Loudoun becomes the fifth county in the Washington area with the top Moody's rating, along with Arlington, Fairfax, Howard and Montgomery.

As Loudoun prepares to sell $111 million in bonds today, County Administrator Kirby M. Bowers said the ranking represented the culmination of years of careful efforts to manage the costs associated with the county's burgeoning population.

"It's kind of like a football game," Bowers said. "We've been sitting at the 5-yard line for the last year or two and have finally pushed it over the goal line. The process of getting it there is a long process."

Two other bond agencies, Standard & Poor's and Fitch Ratings, declined to raise Loudoun's ratings, instead reaffirming their ratings of AA+ for the county. "Debt levels are moderate, but capital needs are significant," according to Fitch.