The traditional married-couple family, a diminishing institution in Maryland, is most prevalent in Carroll County and least common in Baltimore, according to 1990 census figures for the state released yesterday.
Married-couple families accounted for almost 70 percent of Carroll County households, while they made up slightly less than a third of Baltimore's households.
However, the number of single-parent families -- a symbol of family disintegration -- increased more in the Baltimore suburbs than in the city during the 1980s. In booming suburban counties such as Carroll and Howard, the growth of single-parent households headed by women easily exceeded the state average.
Scott Fischer, a Carroll County planner, said the county's rapidly growing stock of single-family homes had attracted families from elsewhere in the area.
"People are moving out here with their families to what they perceive as a more family-oriented area," Mr. Fischer said. "There's a lot of single-family or town house development, as opposed to rental units."
At the same time, soaring housing prices have forced young single people to move across the border into Pennsylvania to seek housing they can afford, he said.
The county-by-county breakdown of census data, provided yesterday by the Maryland Office of Planning, also shows that:
* Talbot County, a retirement haven, has the state's oldest population, with a median age of 39.6 years. More than one in five Talbot residents is 65 or older.
* The fast-growing Southern Maryland counties of Charles and St. Mary's are the state's most youthful. St. Mary's residents have a median age of 29.5 years. Almost one in three Charles countians is under 18, and only one in 16 is 65 or over.
* Housing is most costly in the Washington suburbs of Montgomery County and least expensive in Western Maryland's Allegany County.
The median value of an owner-occupied home in Montgomery, at $200,800, is more than four times the $46,700 median in Allegany.
* For the first time, Prince George's County had more overcrowded housing -- units with more than one person per room -- than Baltimore. As overcrowding increased in Prince George's -- to 5.7 percent of occupied units -- it eased in the city.
* Home ownership is strongest in Southern Maryland's Calvert County, where 85 percent of housing units are occupied by their owners. Baltimore is the only jurisdiction in the state where more residents rent their housing than own it.
However, home ownership increased in the city during the 1980s -- as it did across the area.
The value of owner-occupied housing almost doubled in the city, rising more rapidly even than in Baltimore and Harford counties. Still, the city's median housing value of $54,700 remained by far the lowest in the area.
Howard County had easily the highest housing prices and rental costs in metropolitan Baltimore.
As the counties grew, they also aged noticeably.
The city still has more senior citizens than any metropolitan county, but a larger chunk of Baltimore County's population -- about one in seven residents -- is now 65 or over.
Indeed, the growth of both the elderly population and the number of children under 5 in the Baltimore suburbs exceeded state averages.
In Baltimore County, where the overall population edged up only 5.6 percent over the decade, the number of children under 5 increased by 32.5 percent and that of seniors by 39.7 percent.