Wohlsen was appointed interim mayor in 1979 after Mayor Richard M. Scott resigned to serve as adjutant general of Pennsylvania. Wohlsen was a Republican, and was one of several candidates, including Scott, that the state Republican Party had compelled to join the political arena from the private world during the early 1970s and 1980s. Wohlsen's first challenge as mayor was dealing with a major snowstorm that struck the city during his first day in office. Only a few weeks into his mayoral term, the 100-ton Three Mile Island Nuclear Generating Station experienced a partial meltdown. Despite his experience in the construction business, Wohlsen acknowledged he did not know enough about nuclear power to appreciate the seriousness of the accident. Nobody from Governor Dick Thornburgh's office attempted to communicate with Wohlsen or any Lancaster officials the day of the meltdown. Wohlsen considered and started to prepare the evacuation the city's 57,000 residents as a result of the meltdown, but ultimately did not. Other city officials encouraged him to order elderly residents of high-rises to travel to their families ahead of a general evacuation, but Wohlsen refused, concerned it would incite panic. Wohlsen himself declined to leave the city, claiming, "I felt it was my responsibility to stay here and see what happened. To be the last one to leave the ship."