Letter from St. Louis.

St Louis, the French-founded Midwest city, was once extremely rich - but a combination of the power of Chicago, ill-advised planning decisions in the 1950s and flight of the prosperous to the suburbs has caused a collapse of the centre as disastrous as anywhere in the US. Yet Tom Heneghan holds out hope.

Depending on your view, it's the city of Chuck Berry, Mark McGwire (a baseball player of some repute), Budweiser, Saarinen's arch, or the infamous Pruitt-Igoe housing estate. 'Modern Architecture died on July 15th 1972, at 3.32pm', wrote Charles Jencks, citing the moment when Pruitt-Igoe was demolished by explosion. Jencks was overstating matters, but there is no denying that Pruitt-Igoe and its like have come close to causing 'the death of the city', or at least the death of this city.

St Louis, on the Mississippi river, was the first real Midwest city (Chicago being a usurping latecomer), and it was, for millions of pioneer settlers, 'the gateway to the west' (a title commemorated by Saarinen's beautiful arch). From supplying goods to passing settlers came massive profits, and the construction of elegant streets, palatial dwellings and magnificent warehouses, factories and bridges. Many of these still remain. St Louis retains fine buildings from all the major periods of US expansion, unlike most other cities which were not yet existing in the early nineteenth century, or which have erased their legacy from that time. Unfortunately, 1950s 'urban renewal' removed many elegant old working-class streets, which had become slums, and replaced them with vast, modern, institutionalized slums, like Pruitt-Igoe, which have themselves since been torn down, but only after having destroyed not only the lives of their inhabitants but also the urban fabric of this historic city. Downtown St Louis now has the blitzed, gap-toothed appearance of many modern American cities - with buildings standing alone or in small groups, often unoccupied, surrounded by empty plots and surface car parks, with no one walking in the streets.

It's an impossible problem which was addressed recently by a conference at the architecture department of Washington University in St Louis. Since up to now all architects and planners have been educated in design programmes which have assumed continuous economic and urban growth, the questin is whether we have been adequately equipped to understand and design for conditions of urban 'under-crowding', depopulation, and negative economic growth.

But perhaps, in America, where to some even regional planning suggests the shadow of 'totalitarianism', market forces will continue to shape the environment. Twenty years ago Chicago was much the same as St Louis is today. In the 1960s it experienced a mass - exodus people were deserting a harsh city which seemed to have no future. Now, there is huge immigration into Chicago, which has become, at least partially, a bustling, friendly, and comparatively beautiful and safe metropolis.

Signs of such a rebirth are beginning to appear in St Louis. City centre land values have become low enough to attract young start-up companies, usually hi-tech, and there are enough empty warehouses to satisfy every loft-apartment-seeking yuppie in the Midwest. One recent projection by the Brookings Institution shows the downtown residential population of St Louis increasing by 32 per cent between now and 2010. (Seattle has a predicted 121 per cent increase, Denver 166 per cent, and Houston a predicted 303 per cent increase.) In contrast to the inertness of the civic leaders, some of the old families, old institutions, and a few wacky local residents, are, in a totally uncoordinated way, beginning to create a new vision for the city. At 'The City Museum', husband and wife artist team Bob and Gail Cassily have taken over a huge warehouse and inserted a bizarre and ever-growing, collection of salvaged architectural elements, carved-stone dragons and serpents, an aquarium, a circus, art classes, exhibition spaces, cafes, a model steam-train ride, etc, etc, and even more indescribably etc, producing a building of vibrant urban energy and enjoyment that would leave the burghers and curators of the Centre Pompidou stunned and humbled.

Nick Grimshaw has been invited to design a new botanical research building for Washington University, where Fumihiko Maki is also making a large new architecture and arts building, adjacent to Steinberg Hall, which was his first USA commission many years ago. Downtown, Tadao Ando's new Pulitzer Gallery is rising, exquisitely crafted, with site-manager Peter Clarkson, from Yorkshire, promising the finest concrete walls ever built, anywhere. And, on the adjacent site, will be a new gallery for St Louis"Forum for Contemporary Arts' to be designed by architect Brad Cloepfil, from Oregon, who was selected after a lengthy international competition in which the invited shortlist of eight were required to 'make their pitch' at open lectures in the school of architecture, in front of the judges, with students and faculty listening in facing each speaker with the problem of how to hustle the job while retaining at least some intellectual cred. It was a problem of 'manners', which did not much crease the brow of Rem Koolhaas, who was not in fact invited to the shortlist, but who was there anyway, having formed an alliance with Herzog and de Meuron, who were invited.

Koolhaas' unexpected gatecrashing had a slightly bull in a china shop character. The Forum will be substantially funded by the Pulitzer Foundation, and the originally short-listed architects - such as Peter Zumthor, Gigon and Guyer, and Herzog & de Meuron appeared to have been chosen because of the subtlety of their past works, and the assumption that they could produce a building of great quality that would be different from, but not upstage, its quieter neighbour - Ando's Pulitzer Gallery. Reticence has not often, been a characteristic of Rem's work.

H&deM+OMA were clearly the Dream Team, Koolhaas saying in his lecture that their collaboration was ideal, since he was good at designing horizontal planes, and H&deM were good at vertical ones. But - so the story goes - Rem and Jacques managed to offend the judges by discussing them and their city in French (which they presumably assumed the locals could overhear but not comprehend - an error in a city named after a French king!) And then Zumthor said he didn't like the site or the budget. And then Brad Cloepfil won, and a star is born. The lengthy and very public competition raised expectations that the selection committee, including Terry Riley, MOMA's architecture curator, would be able to appoint an architect of international standing, which is what Cloepfil - not yet a household name - must now become, whether he likes it or not.

But, perhaps more important than all of these projects, in terms of the future of this city, is the work being done now in the old, run-down Soulard district, by the legendary South African Jo Noero, who after years as that country's most significant architect, has been persuaded to join Washington University as Director of Graduate Studies. In Soulard he is working on a number of community-based projects aimed at inserting distinguished but affordable row-houses into the gaps in the old town, aiming to heal the urban fabric and the fragmented local community. It's work which, as Noero says, critics often deride as granola rather than architecture. It's a kind of snob-intellectual architectural segregation at which Noero waves two fingers - having recently won the international competition for the design of the Apartheid Museum at Port Elizabeth, with a design that is at once extremely sensitive to its location, hugely poetic, metaphorical, reticent and expressionistic. It's a tour de force without parallel.

Tom Heneghan is a British architect in Tokyo, Japan, where he is also a professor at Kogakuin University. During the spring semester he was the Ruth and Norman Moore Visiting Professor at the architecture department of Washington University in St Louis.