Over the past decade, Maryland's population grew far more diverse, while growth slowed dramatically in once-booming counties in the Baltimore area, according to data released Wednesday by the Census Bureau.

Baltimore lost more of its population — about 4.6 percent — than any other major city or county in Maryland. The continued decline dashed the hopes of local officials, who had been optimistic that the data would show the city had retained nearly all of its population or even added residents.

Mayor Stephanie Rawlings-Blake noted in a statement that the 2000-2010 decline of about 30,000 residents was the smallest since the 1950s, but said "we have more work to do to get Baltimore growing again."

Meanwhile, many suburban areas continued to expand. Washington's distant southern suburbs grew by more than 20 percent — more than twice the rate of the state as a whole. The fastest growth in the Baltimore area came in Howard, Harford and Carroll counties, although even there, growth rates were slower than in the 1990s.

All of Maryland's growth was due to expanding minority populations, as Hispanics more than doubled and the number of non-Hispanic whites dropped. Non-Hispanic whites now make up less than 55 percent of Maryland's 5.8 million people, compared to 65 percent of the state in 2000.

The demographic changes can be seen at the city's Hampstead Hill Academy. Principal Matthew Hornbeck, whose school includes residents of Fells Point, Washington Hill, Canton and Highlandtown, said nearly a third of the students are Hispanic and have roots in Guatemala, Mexico and Honduras. Just eight years ago, he said, 3 percent of his students were Hispanic.

"People generally continue to think of Baltimore as black and white," he said. "In the southeast, nothing could be further from the truth."

Indeed, though both the black and white populations in Baltimore decreased by around 20,000 each in the last decade, the numbers of Asians and Hispanics increased, complicating the city's historic black-white divide.

Census figures are closely watched because they will be used to redraw the state's political lines and to direct the flow of hundreds of billions of dollars in federal aid. Maryland's population grew by about 9 percent since 2000, but some areas expanded much faster, and that could shift political power away from Baltimore.

The city's population declined to about 621,000, a significantly larger decrease than officials had anticipated. According to early calculations, the population declined so much relative to the rest of Maryland that the city could lose one of its six Senate seats in the coming statewide redistricting.

"We still have a lot to consider," said House Majority Whip Talmadge Branch, an East Baltimore Democrat. "We are going to look at every possible angle before we concede."

Instead, political clout could shift to places like the city of Frederick, which had a nearly 24 percent jump in residents, or to the fast-growing counties around Washington.

State law requires that Maryland's senators each represent roughly the same number of people. Ten years ago the ideal Senate district included 112,691 people. The new ideal size for each seat is 122,842 — which would give Baltimore five seats.

But Maryland still needs to adjust the census data released Wednesday to include prisoners, because a new state law requires incarcerated people to be counted at their last known address. Around six in 10 of the approximately 23,000 state prisoners are from Baltimore. The adjustment process could take until mid-March, officials say.

The new census data could also affect City Council redistricting — Rawlings-Blake had based her proposal on data that assumed a loss of just 20,000 residents.

City officials had not determined Wednesday whether the Census data would require significant changes to the proposed districts. Rawlings-Blake has pledged to amend the plans if necessary; the city charter required that the plans be submitted by Feb. 1, before the new data was available.

While the city's population slipped, area suburbs continued to expand.

Howard County grew by nearly 16 percent, fueled by a large increase in its Asian population. Growth was slower in Baltimore County — just 6.7 percent — but the county is still one of the state's most populous, with more than 800,000 people.

In the southern part of the state, St. Mary's and Charles counties recorded the fastest growth. Montgomery County, still Maryland's most populous county, added nearly 100,000 people during the decade, reaching almost a million residents.