But that law addresses only traffic violations, and some here worry that St. Louis County municipalities are turning to nontraffic fees and fines to make up the lost revenue. In the case of Pagedale, Mr. Maurer said he believed the city had begun doing that years ago when an earlier limit on traffic revenues was imposed. In the mid-1990s, the traffic-fine cap had been 45 percent until legislation began gradually reducing it.

“I think it’s appropriate for policy makers to be mindful that there may be another wave of profiteering that manifests itself in a different form, and continues to create a cycle of poverty,” Eric Schmitt, a Republican state senator who had pressed for the tougher limits on traffic fines, said in an interview. “If we see that, all options are on the table.”

The practice of many St. Louis County municipalities of using traffic and nontraffic fines and fees to finance their budgets has also led to calls for some of those towns to consolidate operations as a means of reducing government costs. A commission assigned by Gov. Jay Nixon to study the underlying causes of the Ferguson unrest issued a long list of recommendations that included consolidating some of the 60 police departments and 81 municipal courts that serve the county.

Residents here say leaders in Pagedale, a predominantly black city of trim homes and about 3,300 people a few miles south of Ferguson, pride themselves on the city’s appearance and on a recent burst of new development, which includes a grocery store and a movie theater that was set to open this week. Some spoke with pride of the city’s Police Department and carefully kept sidewalks.

Yet in recent years, some here say, warning notices have begun appearing on house after house. In 2013, the city generated 17 percent of its $2 million in revenue from all fines and fees, documents show, though Mr. Alton said the portion was lower now. According to an article in The St. Louis Post-Dispatch that first described the rise in nontraffic cases in the region’s municipalities, Pagedale officials issued 495 percent more tickets and citations unrelated to traffic in the years since 2010. City officials dispute that claim, saying the increase was smaller.