Ladd Observatory was opened on October 21, 1891. When Winslow Upton came to Brown as professor of astronomy in 1884, it was understood that the University would build an observatory. When that did not happen, Upton told President Robinson that he might have to go elsewhere. Fortunately, the observatory was forthcoming through the munificence of Governor Herbert W. Ladd and the suggestion of Robinson. At the dedication, Ladd recalled, “Becoming a resident of Rhode Island, my attention was drawn to Brown University, and my interest aroused in it; and when, at the Alumni dinner of 1889, in reply to a question as to what the university most needed, I was informed ‘an observatory,’ and, as circumstances seemed fitting, I determined to make the promise, which was at that time announced.” The site chosen was an elevation about a mile from the University known as “Tin-top Hill” for its use as a depository for old tin cans which, reflected in the sunlight, could be seen from a distance. The land, which was the highest point in a neighborhood of few houses and well suited for the observatory, was purchased by Frank W. and Knight D. Cheney, silk manufacturers of South Manchester, Connecticut, and given to the University. Construction began in May 1890 of a 43 by 27 foot building of brick and stone with a dome 21 feet in diameter made of copper sheets on a steel framework. Inside, a masonry pier, independent of the main building around it, supported the telescope, a refractor of twelve inches aperture and fifteen feet focal length. Its lens was designed by Professor C. S. Hastings of Yale and made by John A. Brashear of Pittsburgh. The German-type equatorial mounting of the telescope and the clock drive which made the telescope revolve were made by G. N. Saegmuller of Washington. An ell, 15 by 25 feet, at the rear of the building contained two transit instruments and two shutters on the roof for their use. The flat roof of the main building enclosed by a railing was designed to be accessible from the tower and to be used for observations by large classes.
Four hundred people, including some well-known scientists, attended the dedication of Ladd Observatory. Since the observatory would not hold them, the exercises took place in a tent on the lawn. Professor Upton delivered an address on “Ancient and Modern Observatories.” In 1893 the University purchased two lots which extended the eastern boundary of the property.
From the beginning the observatory had three purposes, instruction in astronomy for the students, service to astronomical research, and furnishing of time signals. From 1893 to 1973 Ladd Observatory provided time signals, first to the Rhode Island Electric Protective Company, which distributed them throughout the state, then in 1906 to the local fire stations. The transit observations were discontinued in November 1916 and began again after the war in 1919. In 1944 the Observatory began to test the Civil Defense air raid signals at the fire stations every day at noon. The observatory continued to send out its time signals for years, discontinuing the practice only when it was observed that no one was receiving them. The observatory also kept weather records. Alexis Caswell had begun these records in 1831 and kept them for 45 years. The records were kept by the City Engineer after 1876, the observatory after 1890, and the United States Weather Bureau beginning in 1904.
After the death of Upton in 1914, the observatory came under the direction of professors of mathematics R. G. D. Richardson from 1914 to 1921, and Clinton H. Currier from 1921 to 1931. Professor of astronomy Charles H. Smiley took charge for the next forty years, and on his retirement the observatory became the responsibility of the Physics Department, and was directed by Phillip J. Stiles from 1970 to 1986 and by Hendrik J. Gerritsen from 1986 to 1989. David M. Targan became director in 1989. When Ladd Observatory celebrated its one hundredth anniversary on October 21, 1991, a tent adjoining the building was once more required to hold the visitors.