Philadelphia is a city of firsts and foremosts. It was not only this nation's first capital but the site of the first decorative sculpture built with public funds, William Rush's ''Water Nymph and Bittern.''
The two firsts are not unrelated, for it is predictable that a city as redolent with history as Philadephia should muster both the resources and the inspiration to memorialize its heritage.
Since the installation of Rush's fountain in 1799, Philadelphia has steadily shored up its position as the foremost purveyor of urban sculpture in the United States.
The Fairmount Park Art Association, formed in 1872, helped assure the city's preeminence. Charterd by the Commonwealth of Pennsylvania ''to promote and foster the beautiful in the City of Philadelphia, in its architecture, improvements and general plan,'' the FPAA was the first association of its kind in this country.
Its initial purpose, as its name suggests, was to embellish Fairmount Park, the largest urban park in the country, but it proceeded to stud the rest of the city with major works as well. Among the best-known sculptures for which the FPAA is responsible are Antoine-Louis Barye's ''Lion Crushing a Serpent,'' John J. Boyle's ''Stone Age in America,'' Frederic Remington's ''Cowboy,'' and Alexander Stirling Calder's ''Swann Memorial Fountain.''
More recently, Philadelphia's urban sculpture movement received a tremendous infusion of energy from two landmark resolutions passed in 1959. One was a Philadelphia Redevelopment Authority stipulation that any redeveloper of city property ''provide fine arts equal in cost to 1 percent of the total amount spent for construction.'' And nine months later the mayor signed a city ordinance requiring the ''aesthetic ornamentation of city structures'' at a cost of 1 percent of the given construction contract.
The purpose of these resolutions was to heal the breach between art and architecture and integrate them into an aesthetic whole. Michael von Moschzisker , chairman of the redevelopment authority board, maintained, ''Ideally the work of art should be a focus 'round which the harmony of the whole building revolves -- inseparable from the design and aesthetically essential.''
Since 1959 sculptures have proliferated in the cityscape like trees in a forest. Redevelopers working under the authority's mandate have installed approximately 450 sculptures, and the figure for sculptures installed under the city ordinance is about 220.
The federal government has also contributed to the city's avalanche of sculpture through the General Services Administration's Art in Architecture program, which requires that one-half of 1 percent of the cost of federal buildings be spent on artworks for them, and the ''Art in Public Places'' program of the National Endowment for the Arts.
The result of this legacy of private and public support is that Philadelphia, on the proud occasion of its tricentennial, possesses more public sculpture than any other city in the United States. It has served as an inspiration to 35 American cities, such as Seattle, Miami, Chicago, Boston, Atlanta, Baltimore, Milwaukee, Honolulu, and Anchorage, Alaska, which have adopted their own 1 percent laws.
The 1 percent law has not only brought a lot of sculpture to Philadelphia, it has worked exciting changes in the kind of sculpture that is being installed.
Charles Madden, an artist member of the Art Commission, refers to the ''kaleidoscopic'' styles, ''the eclecticism and catholicity of taste,'' that have developed during the 16 years he has been a member of the commission.
He gives as an example the recent installation of Joseph Brown's social realist depiction of ''Benjamin Franklin, Craftsman'' in the square around City Hall, which is well within view of Claes Oldenburg's ''Clothespin,'' in front of Centre Square, a two-tower high-rise.
The clothespin is certainly the most notorious and controversial of the redevelopment authority's commissions, praised by Mr. Madden as ''the mundane made monumental'' and by Anne d'Harnoncourt, curator of 20th-century art at the Philadelphia Museum of Art, as a ''grand example of an increasing interest in relating the work of art to the site in which it is placed or designed for. . . . Both the artist and developer Jack Wolgin were aware of the wonderful, strong vertical responding to the tower, and the contrast of the rich brown material responding to the glass around it.''
City Hall is the center of the city and an aesthetic focal point as well. At the time of its construction in the late 19th century it boasted ''the most ambitious sculptural decoration of any public building in the United States,'' according to an FPAA publication.
Today the salmagundi of contemporary sculpture that encircles it provides not only a striking contrast but a sampler of diverse sculptural styles.
One of them is Robert Indiana's original ''LOVE'' sculpture (it's hard to believe there ever was an original) donated to the city by Fitz Hugh Dixon, city Art Commission president, through a residual family trust established for the betterment of the city.
Situated in the center of a pavilion with its silhouette framing the Benjamin Franklin Parkway the sculpture is too familiar to need comment by anyone other than Mr. Dixon who declared, ''The city's greatest acquisition was my purchase of the 'LOVE' statue because that word should mean more to us than anything else.''
Of course it is not only the City Hall area that is so lavishly festooned. Society Hill, the Universiy of Pennsylvania campus, Penn's Landing, Fairmount Park, the Benjamin Franklin Parkway and Philadelphia Museum, and Independence Mall all possess stunning examples of outdoor sculpture too numerous to mention.
The interested visitor to the city would be well advised to procure as quickly as possible either ''Urban Encounters,'' a walking-tour map of public art from 1959 to 1970 published by the Institute of Contemporary Art and available free at the John F. Kennedy Tourist Center or ''Philadelphia's Treasures,'' a guidebook published by the FPAA.
Significant trends have emerged in Philadelphia's sculpture renaissance. ''There's a flexibility and an ingenuity in terms of what sculpture can be,'' says Miss d'Harnoncourt. Sculpture no longer has to be a historical monument commemorating an event or personage but may instead be witty or whimsical, as personal or abstract as the form it sometimes assumes. Sculpture has also tended to climb down off its pedestal in search of a greater intimacy with the people and the architecture that surrounds it.
Whether the piece is as abstract as Tony Smith's ''We Lost'' or as figurative as George Segal's ''Woman Looking Through a Window,'' these contemporary sculptures elicit a far greater degree of involvement from the viewer than did the traditional 19th-century statues.
Mary Kilroy, a member of the redevelopment authority's advisory board of design, cites as the most important recent trend ''a more environmental approach to art,'' which encourages the use of many different kinds of materials, some of them unusual.
The environmental aesthetic was the theme of an influential exhibition at the Pennsylvania Academy of the Fine Arts earlier this year, sponsored by the FPAA as a part of the city's tricentennial.
The thesis that gradually emerged from the exhibition, ''Form and Function: Proposals for Public Art for Philadelphia'' was that of the integration between art and life or form and function.
In other words, sculpture does not belong on a pedestal or sequestered in a museum but in society as a part of our architecture and our environment, as has been commonplace in other cultures.
For the exhibition the FPAA elicited proposals for works on specific sites from contemporary sculptors whose work inclined in an environmental direction.
The proposals included Rafael Ferrer's aluminum and epoxy paint ''El Gran Teatro de la Luna,'' designed to encircle like a crown the top of a public lavatory in a Hispanic neighborhood; fluorescent lights along the Falls Bridge which spans the Schuylkill River by Dan Flavin; Robert Irwin's ''Philadelphia Stoop,'' a stairway in the round with a tree growing out of the center, for City Center; a bridge by John Hejduk; a pier by Jody Pinto; and a ''Pavilion in the Trees'' by Martin Puryear. (These are all works in progress, and as of this writing only Mr. Ferrer's has been approved for construction.)
Sculpture in the past was primarily decorative,'' according to the exhibition's guest curator, Penny Balkin Bach. ''There have been singular instances of functional sculpture woven into the city, but they are few. What this exhibition tries to do is demonstrate how the work of sculptors can be integrated with city planning and the life of the city and also how artists can be committed to and involved with the life of the city. Much of contemporary sculpture is difficult for people to grasp but these works bridge the gap.''