Being one of few Iowans capable of telling time from the stars, Horr was appointed the official regulator of the town clock, a position he held for twenty years. One of the leading surgeons in eastern Iowa, Horr was also a prominent supporter of building the original TOWN CLOCK. The longitude of Dubuque was determined using his astronomical transit.
Between 1851 and 1871 Horr measured the rain and snowfall, recorded the temperature in the city and reported his information to the Commissioner of Patents and the Smithsonian Institution. His reports often carried unusual additional comments concerning the amount of river ICE, notes about the bird migrations, and remarks about the success of the harvests. He was gradually eased out of the weather gathering business by the government as the United States Army Signal Corps took charge in 1873.