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​PA-SHARE Data Quality

This data quality statement is under development and will be refined as more information becomes available through PA-SHARE.

The Pennsylvania Historic and Archaeological Resource Exchange (PA-SHARE) includes a map-based inventory of the historic resources, archaeological sites, surveys, historical markers, and program-related information stored in the files of the Pennsylvania State Historic Preservation Office (PA SHPO). PA-SHARE is the PA SHPO's chief storehouse of information and includes an ever-expanding number of digital records. The Pennsylvania Historical and Museum Commission (PHMC) has been collecting information concerning historic places and archaeological sites for the greater part of a century. Data gathered in PA-SHARE enables the PA SHPO to fulfill its responsibilities most effectively and efficiently as well as prioritize actions to assist partners and the public in achieving preservation outcomes.

Data in PA-SHARE are reflective of the quality of the data as submitted to PA SHPO. Historic resources and archeological sites within PA-SHARE may not include precise boundaries because of various sources and ages of mapped data and should be considered advisory for planning purposes, pending field verification. Absence of data does not necessarily indicate absence of resources or other program-related information. PA-SHARE is an ongoing initiative, and tables and associated data will undergo staged enhancements and constant updating. From 2017 to 2019, PA SHPO digitized historic and archaeological resource records and reports held within the PA SHPO file room and these are now available online via PA-SHARE. Visible data may be dependent on PA-SHARE subscriptions. 

Archaeological Sites

Archaeological sites are added to the Pennsylvania Archaeological Site Survey (PASS) whenever site forms are received from any source. There has not been a full systematic archaeological survey of the Commonwealth. Environmental data for archaeological sites are often extrapolated from maps. Locations are not field verified by SHPO personnel prior to inclusion. Site information frequently reflects only the initial investigation of the site. Information from subsequent excavations is added when provided, but many researchers do not submit updated forms.

To be included in PA-SHARE, sites must meet our Site Identification Criteria and will be assigned a Smithsonian trinomial, which we call a PASS number, formatted as 36XX0000 where 36 represents Pennsylvania, the two-letter code is the county designation, and the four numbers represent the sequence number of the site within the county. Isolated finds and non-site collections are designated by 36XX/000. These are generally locations where individual diagnostics were found, or where materials were collected that do not meet the site criteria but were included in the curated collections from a project.

All archaeological sites that had map locations that provided locational data have been mapped. All boundaries should be considered approximate unless the site has been fully excavated. Any site showing on the map as a small circle is represented by only a center point. This was very common on early records. Approximately 140 records have no locational information.

Statewide Pre‐Contact Probability Model

The Pennsylvania Department of Transportation (PennDOT), in partnership with The Federal Highway Administration (FHWA), through a research grant, and in coordination with Pennsylvania State Historic Preservation Office (PA SHPO), developed The Statewide Pre-Contact Probability Model (Model). PennDOT contracted with URS Corporation (now AECOM) to develop the Model with the intent to provide better data to regional transportation organizations (i.e., metropolitan planning organizations [MPOs] and rural planning organizations [RPOs]) to aid in decision-making as part of PennDOT's Linking Planning & NEPA (now known as PennDOT Connects).

The Model involved developing statistical models to analyze the landscape at known pre-contact Native American archaeological sites in Pennsylvania and extrapolating identified patterns to all areas of the Commonwealth of Pennsylvania. Due to the variability of environments and pre-contact Native American cultures throughout Pennsylvania, many different models were produced for different areas. One of the major accomplishments of the Model is a complete statewide layer of archaeological sensitivity aggregated from 132 spatial subareas. The Model only evaluates the potential for pre-contact sites. The probability of the presence of contact period and historic archaeological sites should still be evaluated using historic documentation.

Statewide Pre-Contact Probability Model Geographic Information System (GIS) layers are available to registered users of PA-SHARE with archaeological privileges. This Model layer is intended to be used as a planning tool in concert with other planning tools and is not a substitute for consultation with the PA SHPO, nor is it a substitute for site-specific professional judgment.

Because the individual sub-models do not account for modern development, the probability layers that have been generated should always be viewed on base maps of aerial photography as well as any other documentation of disturbances. In addition, the PA SHPO does not treat the model as absolute, as it requires updating through the results of on-the-ground testing in various parts of the state.

Environmental Reviewers at PA SHPO have noticed differences in the accuracy among regional models. Some of this may be due to some regions having a much larger population of recorded sites and surveys than others; in other regions that have been well surveyed, the reasons are not clear. It is the intent that accumulated results of ongoing testing of the model will eventually result in having the updated information run again to refine the accuracy.

Above Ground Resources 

Above ground resource information is received from many sources: municipal surveys, environmental review surveys, thematic studies, and individual property submissions for environmental review or National Register consideration. Not all of Pennsylvania's 67 counties have been systematically surveyed. New above ground resources are entered and mapped when received and new surveys received electronically may have a delay in the uploading process for data verification and conversion. 

Data associated with above ground resources include property and cultural information that was captured by the person documenting the historic resource. Data reflects the condition and known information of the above ground resource at time of recordation. The completeness of the locational data varies by county.

Mapping of above ground resources has fluctuated over the years. Prior to 1996, each building had its own number and mapping. Between 1996 and 2020, only the resource that would be evaluated for the National Register of Historic Places was mapped and given what we called a Key number. This means that, in the case of a district, the district boundaries would be mapped, not the individual buildings on the inventory. We actively consolidated some of these older districts and removed the individual mapping. With PA-SHARE we have returned to mapping individual buildings. As a result, some districts will show all their "child resources," meaning, the individual buildings, and some will not.

Archaeological and Historic Survey and Reports

Our Reports data set includes many types of documents that describe cultural resource management work. Surveys are a set of data that involve investigations at particular places, which may result in a Report.

Most of the legacy reports in PA-SHARE are the result of environmental review surveys. These reports are identified by their legacy project file "ER Numbers" which have a format of YYYY-NNNN-CCC-A; the first 4 digits are the year the project started, the second four are a sequence number within that year, the next three are the county code, and a final (optional) letter indicates the submission within that project.

Other report types include reports from regional surveys, multiple property nomination (thematic) documentation, historic context documents, and research papers.

Only Phase I archaeological surveys, geomorphological reports, negative survey forms, and records of disturbance were mapped. Since Phase IIs and IIIs are, by definition, within recorded sites, these reports were not mapped. Quality and granularity of the mapping is dependent upon the quality of the original mapping. Older reports tend to show only generalized areas. Newer reports will have specific testing areas mapped.

Historic Resource Survey Reports often cover entire municipalities or even counties and therefore were not mapped in the previous GIS system.

Historical Markers

The data in the Historical Markers data set includes information related to the text on the marker, its date of installation, municipal locations, and subject matter categories. Mapping is based on points derived from the recorded latitude and longitude of the marker.


Legacy Project data for environmental reviews have been migrated from a system begun in the early 1980s and include limited information. No legacy projects were mapped. Going forward, all Areas of Potential Effect will be mapped and visible to PA-SHARE registered users.