[1] Contemporary scientists estimated the size of the sunspot (AR1842)[1] which began on May 10—and caused the storm—as 151,000 by 34,000 km (94,000 by 21,000 miles).

[3][4] The storm was extensively reported in New York City, which was a center of telegraph activity as a railroad hub.

[5] Auroras ("northern lights") appeared throughout the eastern United States, creating brightly lit night skies.

Telegraph service in the U.S. first slowed and then virtually stopped at about midnight on 14 May due to blown fuses and damaged equipment.

[6] Radio propagation was enhanced during the storm due to ionosphere involvement, however, enabling unusually good long-distance reception.