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Opening a Critical Piece of City Infrastructure
In January 2011, San Francisco released its Enterprise Addressing System as open source software, making one of the most fundamental pieces of urban data infrastructure freely available to other jurisdictions. The Enterprise Addressing System, or EAS, is a web-based tool for managing a city’s master database of physical addresses, linking each address to assessor parcels and the street centerline network.
Address management might sound mundane, but it underpins virtually every government function that involves location. Emergency response, tax assessment, utility service, permit processing, election administration, and census operations all depend on accurate, authoritative address data. When address records are inconsistent or incomplete, the effects ripple across every department that relies on location information.
What the Enterprise Addressing System Does
EAS provides a centralized system for maintaining the official record of addresses within a jurisdiction. Its core capabilities include:
- Address creation and validation ensuring new addresses conform to established naming and numbering conventions
- Parcel linkage connecting each address to the corresponding assessor parcel record
- Street network integration tying addresses to the geographic street centerline data that routing and mapping systems depend on
- Change management tracking address modifications, retirements, and reassignments with full audit history
- Cross-departmental access providing a single authoritative source that all city departments can reference
The system was developed over approximately eighteen months of internal work by San Francisco’s GIS and IT teams, led by programmer Paul McCullough and GIS manager Jeff Johnson.
Why Open Sourcing Mattered
After San Francisco demonstrated the EAS in a public screencast, significant interest emerged from other jurisdictions facing the same address management challenges. Rather than waiting until the system was in full production, the city made the decision to open source the code immediately, recognizing that early access would allow other agencies to evaluate the software and begin planning their own deployments.
The open source release was handled thoughtfully:
- Full development history was preserved when the code was moved to a public repository, giving outside developers visibility into the project’s evolution
- Bug tickets and documentation were transferred alongside the source code
- A setup script was created to help new developers turn raw source into a deployable application
- A discussion group was established for users to ask questions and share experiences
This approach reflected a growing understanding in civic technology that code dumps, simply publishing source code without context, are far less useful than structured releases that include the documentation and community infrastructure needed for practical adoption.
The Challenge of Multi-Jurisdictional Deployment
The EAS had been developed to meet San Francisco’s specific requirements, running within San Francisco’s technical environment and tuned for its particular data structures and workflows. Making it deployable in other jurisdictions required additional work to identify and document dependencies, create configuration options for different environments, and improve the installation process.
This is a common challenge in government software sharing. Systems built for one agency’s needs rarely work out of the box in another agency’s environment. Successful sharing requires deliberate investment in portability, documentation, and community support, investment that goes beyond the original development scope.
The long-term vision for EAS was a multi-jurisdictional system that could be deployed and customized by different cities and counties, each maintaining their own address data while building on a common software foundation. This vision reflected the broader civic commons philosophy: build once, share widely, and let each adopter adapt the tool to local needs.
Broader Significance
The EAS open sourcing illustrated several important themes in civic technology:
Infrastructure Software Matters
Much civic technology attention focuses on citizen-facing applications like mobile reporting tools and transparency dashboards. But the underlying data infrastructure that these applications depend on is equally important and equally deserving of open, shared approaches. Address management, parcel data, street networks, and other foundational datasets are the hidden infrastructure of modern government operations.
Early Release Beats Perfect Release
San Francisco chose to open source EAS before it was in production, when there were still known issues to resolve and documentation to complete. This decision allowed other jurisdictions to begin evaluating and planning while the software was still actively being improved, rather than waiting for a polished release that might never come.
Government-to-Government Sharing
The EAS story demonstrated direct government-to-government software sharing, one city building a tool that other cities could adopt. This peer-to-peer sharing model is one of the most straightforward paths to reducing duplication in government technology spending.
The project reinforced the principle that city-developed software, funded by taxpayers and designed for public purposes, belongs in the public domain where other communities can benefit from the investment.