It was hardly a secret as Dayton moved into the early 1970s that it was in serious trouble.

Manufacturing and other jobs were pouring away from this industrial center of 200,000 residents. At NCR Corp.; the big computer and business machine firm, some 15,000 jobs were lost, in the worst example of what was happening.

Meanwhile, downtown, the citadel of retailing, was about to face competition that would leave it number two when a a huge new regional center, the Dayton Mall, opened.

Moreover, there were also fears that downtown would lose its preeminence as an office center, possibly to the burgeoning area around the mall.

To avert such changes the city undertook another urban renewal project downtown, its fourth. This one, it was hoped, would be dramatic enough not only to stop the trend away from downtown but to reverse it.

In the fall of 1973, after secret mameuvering by the city to line up the tenants it would need for such a project - huge by Dayton standards - a nationally known developer, John W. Galbreath, unveiled his plan for Courthouse Square.

A little over three years later, a sizeable new department store opened there. It was soon surrounded by two sleek white office towers, one 27 stories tall.

How did the city do it? Part of the answer can be found in the massive infusion of the city's own money into the project. The federal government was no longer funding urban renewal projects, so Dayton picked up almost the whole bill. The cost, when all the bills are in, is expected to come to about $33.1 million.

In return the city got more than $40 million in private investment, more than 200 new jobs, and the assurance that the Mead Corp., a $1.8 billion manufacturing company, would keep its headquarters in town as the prime tenant in the 27-story tower.

But there was more to the project's cost than the city's immediate investment. In the short term, it appears that revenues generated by the project will fall short of what it will cost the city.

By 1977 the cost of interest and and principal on bonds issued to pay the city's share had come to $1.8 million. Courthouse Square had generated less than $550,000. Those revenues included income tax from Mead Corp. employes, who might today be working in the suburbs if Courthouse Square had not been built.

Over the long haul, however, the project is expected to generate substantial revenues for the city, particularly after more than $15 million in property tax breaks - given as an incentive for building Courthouse Square - expire. Throught the year 2040, the city expects that Courthouse Square will yield Dayton more than $26 million over its investment, while producing another $23.9 million for the schools.

In the meantime, the city will use property taxes to make up the difference between Courthouse Square revenues and the payments on the bonds that financed it, a common practice in such cases.

But the size of Courthouse Square was such that the city will have to wait five years before it can take on any sizeable new projects, projects that would require property taxes to help pay off financing bonds, said Louis Zimmerlin, the retired city accountant, who calculated Courthouse Square's financing.

Since Courthouse Square has been completed, the surrounding area has begun to blossom, a spinoff that Courthouse Square proponents had hoped for. Examples include the multi-million dollar renovation of the city's largest department store, plans for two headquarters for savings and loan associations, and the recently begun restoration of the city's shopping arcade.

To date, about a third of the downtown has been urban renewed.