Presented is a list of voltages (electric potential differences) measured during magnetic storms on grounded long lines in the United States and Canada between 1891 and 1940. The sources for the list are published papers, technical documents, and newspapers. Each entry consists of the maximum voltage measured for each storm on a specified line connecting two ground points, nominally, between A "and" B. However, if a specific polarity is available, for example, the positive voltage from point A to point B, then the maximum voltage for the indicated polarity is listed, that is, positive A "to" B; conversely, for the opposite polarity, that is, from point B to point A, then the maximum voltage for the indicated polarity is listed, B "to" A. Per the sources, the list includes brief descriptions of each measurement, the locations of ground points (city/town names), and the date each measurement was made. When given by the sources, start time and end times are also listed. None of the sources include specific locations (latitude and longitude) of the ground points; these have been estimated by the location of the city/town. For each listed voltage, the distance between the ground points and the corresponding average geoelectric field strength are given.
