This data release reports water-quantity and water-quality data collected during 2014-2016 by the U.S. Geological Survey (USGS) and in cooperation with the National Park Service (NPS) at the Allegheny Portage Railroad National Historic Site (ALPO) in Blair and Cambria Counties, Pennsylvania (figure 1). These data establish a base-line for current hydrologic conditions and may be helpful to evaluate potential changes in the hydrologic characteristics of streams and associated wetlands at the ALPO Summit area (figure 2). The data are summarized in the interpretive report, “Hydrologic Characteristics and Water Quality of Headwater Streams and Wetlands at the Allegheny Portage Railroad National Historic Site, Summit Area, Blair and Cambria Counties, Pennsylvania, 2014-2016” by Cravotta and others (in review). During 2014-2016, synoptic surveys were conducted by the USGS, with assistance from NPS, to obtain data on stream flow or stage and the corresponding water quality over a range of hydrologic conditions at 10 monitoring sites (table 1, figure 2). The synoptic surveys typically included measurements of the water level at piezometers and stream gages, plus stream flow at the gages and associated tributary, seepage, or wetland sites. The daily values for data on stream stage (table 2) and piezometer water-level altitude (table 3) and water temperature (table 4) plus the corresponding daily precipitation and air-temperature data for PA13 (table 5) are summarized for this data release and presented with interpretations in the report by Cravotta and others (in review).