Not so long ago, it took Art Helton about 30 minutes, 35 max, to drive from Harford County into Baltimore. Now, because of traffic, it takes him more than an hour.

The reason, he said, is that Harford County has not done an adequate job of planning for the explosive growth that is transforming the once-rural county.

Four years ago, Helton, a Democrat, ran for county executive on the theme of controlling growth. Now he is sounding the same message in his run for the state Senate.

Since 1990, the population in Harford County has grown 20 percent, from 182,132 to 218,590, according to the 2000 census. Much of that growth has been on the outskirts of Bel Air, along Route 24, which links Interstate 95 to the town.

Many of the new residents are from Baltimore City and Baltimore County, and they were attracted by the county's reasonable housing prices and rural character.

But the consequences of that growth have been predictable: Countywide, said Helton, there are 87 portable classrooms. Rush-hour crawls have become a fact of life. And longtime residents fret that their county is losing its small-town character. "We have not been able to provide the public services," Helton said.

But county and town officials note that the growth is taking place as planned, primarily within a "development envelope," as they call it, an area bounded by I-95 or U.S. 40, which are parallel, and Route 24.

"That's where growth can be efficiently and economically accommodated, and that's the whole idea of Smart Growth," said Joe Kocy, the county planning director, a reference to Gov. Parris N. Glendening's initiative to pursue growth in established communities.

County Executive James M. Harkins also sounded the Smart Growth note. "Our strategy has been to push the development to Route 40, which is consistent with Smart Growth strategy," he said. "It's the redevelopment of old areas, not paving over of new areas."

Harkins noted that most of the remaining 5,000 or so lots in that envelope cannot be built on because of wetland or other environmental issues. "The development envelope is about filled," he said.

Growth was a major issue in the county executive race that Harkins won four years ago, and Harkins said he has been working since then to preserve open space and to "play catch-up with the growth we have had in the past."

In his tenure, he argued, no zoning changes were approved to allow more construction. "The zoning we have was created before I came along and we've held to that," he said.

In the past four years, construction has taken place on about 7,500 acres, he said. But the county also worked to preserve more than 8,800 acres through state and county programs that purchase development rights from farmers.

For the first time in the history of the county, he said, more land has been set aside for preservation than has been lost to development. "It's always been the other way," he said.

Still, there's no denying that Harford County has changed from rural to suburban, especially in the southern end. "If you've been here for 10 years or more you've seen a lot of change," said David E. Carey, the mayor of Bel Air, which is at the epicenter of most of the growth.

Although the population of Bel Air has remained fairly stable, "all this growth has happened around us," he said. "In many ways, Bel Air has become a crossroads for the county."

The big problem with that is the traffic. Route 1, which travels through Bel Air, is of particular concern. "At rush hour in the afternoon, and on the weekends, it's often gridlock," he said.

Yet Carey says the quality of life is not eroding. "These are growing pains," he said.

Harkins, a seventh-generation resident of the county, remembers dirt roads and open fields where now there are houses and commercial developments.

But more of those areas are filled with houses than with commercial buildings, and that is creating a strain on the local tax base. New roads, schools and other amenities cost money, and residential development as a rule requires more services than it pays for.

For that reason, Harkins and the mayors of Harford County's municipalities are talking about bringing more manufacturing and technology jobs into the county.

"A lot of it is the economics of luring high-tech businesses or clean industrial ... to Harford County," said Carey.

The county has added 4,500 manufacturing and technology jobs in the past four years, Harkins said. "We're the only county in the state of Maryland to see an increase in manufacturing jobs last year," he said.

Those efforts have been particularly successful in Aberdeen, which has lured several prominent employers in the past dozen or so years, including a Frito-Lay manufacturing and distribution facility and a Saks Fifth Avenue office and distribution center.

Ripken Stadium, which opened this year, has also brought new traffic to the area.

Of the three municipalities in Harford County -- Aberdeen, Bel Air and Havre de Grace -- Aberdeen has seen the smallest percentage of growth over the past decade, said City Manager Peter A. Dacey.

Yet even with a population increase of less than 6 percent, "it's a challenge to keep that small-town feel," he said. With that goal in mind, the city, which recorded a population of 13,842 in the 2000 census, is discouraging high-density housing and apartments in favor of single-family homes, he said.

The schools are far less crowded than in other parts of the county, with Aberdeen Middle School rated at 73 percent of capacity, and many elementary schools having room to spare.

That's not the case in other parts of the county, where portable classrooms have become a familiar part of the school day to many students. Harkins said he is working to build schools that have more capacity than necessary, so they're not crowded the day they open.

Plans are in the works for a middle school and high school in the Bel Air area, as well as expansions to North Harford, Bel Air and Edgewood high schools. The latter school serves the Edgewood and Abingdon areas.

Southampton Middle School, where David R. Craig works as an assistant principal, houses 1,951 pupils, though its capacity is 1,598. Portable classrooms soak up the overflow. But the quality of the school is not suffering as a result, he said.

"Education is about what happens between the teachers and the students," he said.

Craig is in a unique position to chart the changes in Havre de Grace, which grew from about 8,000 residents in 1990 to about 12,000 10 years later: He is serving his second term as its mayor.

During his first term, from 1985 to 1989, the city government had two departments: one for police and one for public works. There were about 80 full-time employees. "We had a city clerk's office with a city clerk and a secretary," he added.

In his second stint as mayor, Craig, who was elected last year, is presiding over a completely different government. Now there are five departments: the original two, plus an Office of Planning, a Finance Department and a Department of Administration. There are 110 full-time employees.

The government has also moved into a different building, one that was built in 1993 and expanded this year. "We're almost getting to the point where we will need a full-time mayor," he said.