Prince George's County Executive Jack B. Johnson looked every bit the proud father announcing a new arrival when he walked to the lectern Friday afternoon.

In this case, the newborn's name is Aa2. That is the county's new bond rating, upgraded from Aa3 by Moody's Investors Service, one of the Wall Street firms that evaluates the financial health of local governments.

Although the improvement looks incremental at best -- ratings range from D to a maximum of Aaa -- it will allow the county to borrow money at more favorable interest rates, potentially saving taxpayers millions of dollars. It also ranks the county in the top 10 percent of local governments, county officials said.

"It's a milestone in the life of Prince George's County," Johnson (D) said during the news conference in Upper Marlboro. "Prince George's is really just beginning to shine. . . . The development community understands it. And Wall Street is beginning to understand it."

Moody's said the higher rating reflects steady improvement in the county's financial performance despite the voter-imposed cap on property tax growth known as TRIM (Tax Reform Initiative by Marylanders). The county's $48 billion tax base -- the total assessed valuation of property in Prince George's -- has grown at an average rate of 4.1 percent annually the past five years, including 7.4 percent and 5.3 percent the past two years.

Analysts expect that growth to continue with such projects as National Harbor, further development of the Boulevard at Capital Centre and the expansion of the Bowie Town Center.

"They have demonstrated a consistent financial performance even though they have the cap," said Lisa Cole, a Moody's analyst. "Then you add the size of the tax base and the growth and development that is going on."

The new assessment by Moody's falls in line with AA ratings from the two other firms that rate local governments, Fitch and Standard & Poor's. Despite the slightly different terminology, officials said, the ratings are equivalent.

Wall Street's confidence in Prince George's began to build during County Executive Wayne K. Curry's tenure, which ended in December 2002. Analysts issued a report at the end of Curry's term concluding that the "county's strong management team" had "demonstrated exceptional fiscal resolve."

Johnson, they said, has shown some of the same fiscal prudence.

"The county is doing very well," said Joseph D. Mason, a Fitch analyst. "The Johnson administration clearly has retained the commitment of living within the revenue limitations imposed by the county voters. . . . There was positive momentum started in the previous administration, and it's continued in this administration."

Johnson, who met last month in New York with financial analysts, said TRIM remains "a huge issue for all of the rating agencies." Once again, he indicated that he eventually will ask Prince George's voters to consider lifting all or part of it.

"This has to be a joint venture," Johnson said. "We have to figure out what we will be asking the citizens for."

Prince George's still lags behind most of its neighboring counties. Montgomery and Fairfax have Aaa bond ratings.

"There are a lot of counties that are richer than us and bigger than us," Johnson said he told the Wall Street analysts. "But if you are going to invest, you should do it not in those that have already arrived but those that have potential."