On 30 July 1891, he became a naturalized citizen of the United States at the age of 35. Tesla established his 35 South Fifth Avenue laboratory in New York in the same year. Later, Tesla established his Houston Street laboratory in New York at 46 E. Houston Street. There, at one point while conducting mechanical resonance experiments with electro-mechanical oscillators, he generated a resonance in several surrounding buildings but, because of the frequencies involved, not his own building, causing complaints to the police. As the speed grew, he hit the resonant frequency of his own building and, belatedly realizing the danger, was forced to apply a sledgehammer to terminate the experiment, just as the police arrived. He also lit electric lamps wirelessly at both of the New York locations, providing evidence for the potential of wireless power transmission.