Philadelphias Grid Plan
Philadelphia's grid plan refers to the original street layout designed by William Penn and his surveyor Thomas Holme in 1682 for the new capital of Pennsylvania. The plan established a regular pattern of streets intersecting at right angles, with two major thoroughfares—Broad Street running north-south and High Street (now Market Street) running east-west—crossing at the center of the city. Penn placed five public squares at strategic locations: one at the center (now occupied by Philadelphia City Hall) and four others near the corners of the original plan (now Rittenhouse Square, Washington Square, Logan Square, and Franklin Square). This grid layout, revolutionary for its time, has defined Center City Philadelphia for more than three centuries and influenced urban planning throughout the United States.[1]
Origins and Design
[edit | edit source]Penn's design for Philadelphia reflected both practical considerations and his idealistic vision for his "Holy Experiment." Having experienced the Great Fire of London in 1666, which destroyed much of the crowded medieval city, Penn was determined to create an urban environment that would resist fire and disease. He envisioned Philadelphia as a "greene countrie towne" where each house would stand in the middle of its lot, surrounded by gardens and orchards, preventing the spread of flames and providing fresh air and sunlight. Wide streets would allow for traffic and airflow, while the regular grid would facilitate navigation and lot division. These practical concerns combined with Penn's Quaker values of order, simplicity, and equality to produce a city plan unlike any in the European tradition.[2]
Penn worked with Thomas Holme, an Irish Quaker surveyor, to translate his vision into a workable plan. Holme arrived in Pennsylvania in 1682 and immediately began laying out the city according to Penn's instructions. The original plan covered approximately two square miles between the Delaware and Schuylkill Rivers, bounded on the north by Vine Street and on the south by Cedar Street (now South Street). Streets running east-west were named for trees and plants—Chestnut, Walnut, Spruce, Pine, Locust, Cherry, Arch (originally Mulberry)—while streets running north-south were numbered, increasing from the Delaware River westward. This naming convention, simple and systematic, reflected Penn's Quaker preference for plainness over the aristocratic naming practices of European cities.[3]
Major Streets and Layout
[edit | edit source]The plan's two principal streets—Broad Street and High Street (Market Street)—were significantly wider than the others, intended to serve as the city's main arteries. High Street, running from the Delaware River to the Schuylkill, was designed as the commercial spine of the city, with a market established in its center from the earliest days of settlement. Broad Street, running north-south, was envisioned as a grand ceremonial avenue, though it would not be fully developed as such until the late 19th century. The intersection of these two streets at Centre Square marked the geometric center of Penn's plan, the site he intended for public buildings and eventually occupied by Philadelphia City Hall.[4]
The numbered streets of the grid begin at the Delaware River and increase westward: Front Street (originally First Street, but renamed because it fronted the river), then 2nd, 3rd, 4th, and so on to the Schuylkill. The major cross-streets—Market, Chestnut, Walnut, and Locust—were wider than the minor streets between them, creating a hierarchy of thoroughfares that distinguished commercial from residential areas. This basic framework remains intact today, though the city has expanded far beyond Penn's original boundaries and development has long since filled in the lots Penn hoped would remain garden plots. The numbered street system has extended into North, South, and West Philadelphia, providing a consistent address system across much of the city.[2]
The Five Squares
[edit | edit source]Central to Penn's vision were the five public squares that punctuated his grid. Centre Square, at the intersection of Broad and Market Streets, was the largest and most important, intended as the civic heart of the city. The four corner squares—originally named simply Northeast, Northwest, Southeast, and Southwest—were distributed near the edges of the plan to ensure that all residents had access to public open space. Penn intended these squares to remain open forever, providing light, air, and recreation for the city's inhabitants. Three of the four corner squares were later renamed to honor prominent Philadelphians: Rittenhouse Square (for astronomer David Rittenhouse), Washington Square (for George Washington), and Logan Square (for James Logan, Penn's secretary). Franklin Square retained its directional name until being renamed for Benjamin Franklin.[1]
The squares have evolved significantly from Penn's original conception. Centre Square was occupied by Philadelphia City Hall beginning in 1871, eliminating the open space Penn had envisioned. The corner squares have been redesigned multiple times, transforming from simple greens into more elaborate parks with fountains, sculptures, and formal landscaping. Rittenhouse Square, in particular, has become one of the city's premier public spaces, surrounded by high-rise apartment buildings and serving as the social center of its fashionable neighborhood. Despite these changes, the squares continue to fulfill Penn's basic intention of providing public green space within the urban fabric, and their locations at the intersections of major streets remain as he planned them.[4]
Diagonal Streets
[edit | edit source]While the grid plan dominates Center City, several diagonal streets cut across it, following routes established by the Lenape and early European settlers before Penn's arrival. These include Ridge Avenue, running northwest from the Delaware River toward Roxborough; Germantown Avenue, running from Northern Liberties through Germantown and Chestnut Hill; and Passyunk Avenue in South Philadelphia. These diagonal streets, based on ancient Lenape trails, create irregular intersections and oddly shaped blocks where they cross the grid, including the famous triangle at 9th and Passyunk that houses the Italian Market area. Rather than obliterating these pre-existing routes, Penn's surveyors accommodated them, allowing indigenous geography to coexist with the imposed European order.[2]
The coexistence of grid and diagonal streets gives Philadelphia a distinctive character among American cities. The regular grid provides navigational clarity and efficient lot division, while the diagonal streets create visual interest, traffic shortcuts, and quirky corner buildings. The small parks at five-way intersections, such as the one at Ridge and North Broad, result from the intersection of diagonal and grid streets. This layering of indigenous trails, colonial planning, and later development creates a palimpsest of urban history visible in the city's street pattern—a physical record of the different peoples and eras that have shaped Philadelphia.[1]
Influence and Legacy
[edit | edit source]Penn's grid plan for Philadelphia was among the most influential urban designs in American history. The grid layout, with its regularity, legibility, and ease of lot division, became the dominant model for American cities from the colonial era through the 19th century. When the federal government sold western lands, it used a grid system derived partly from Philadelphia's example. Cities including New York, Washington (whose diagonal avenues interrupted an underlying grid), Chicago, and countless smaller towns adopted grid plans influenced by Philadelphia's precedent. The idea that cities should be planned in advance, rather than growing organically, became a characteristically American approach to urbanism.[1]
The grid has also shaped Philadelphia's development in specific ways. The regular lot sizes facilitated property development and real estate transactions. The numbered streets provided an intuitive address system that made navigation easy even for newcomers. The reserved public squares ensured that Center City would retain significant green space even as development filled every available lot. And the width of major streets like Market and Broad accommodated the increasing traffic demands of a growing city—though Penn could never have anticipated automobiles, his generous street widths proved adaptable to modern transportation. After more than 340 years, Penn's grid remains the organizing framework of Center City Philadelphia, a testament to the durability and adaptability of his visionary plan.[4]