Founded on the 635-foot summit of Great Blue Hill by Harvard University's first professor of meteorology, Abbott Lawrence Rotch, and partly designed by his brother Arthur, the original 1885 structure consisted of a two-story circular stone tower and an attached single-story residence constructed of stone found at the site. Four years later a two-story library and shop were added; a similar structure of concrete replaced the stone tower in 1908. The observatory is noted for maintaining a long climatological record and for pioneering the use of balloons and kites to carry weather-recording instruments. Wind velocities, air temperature, and relative humidity at various levels became vital elements to weather prediction due to techniques developed at the site. Located within the seven-thousand-acre Blue Hills Reservation, the observatory stands near a massive stone observation tower (NR) named for Charles Eliot, a founder of the Boston Metropolitan Parks System, in 1893. The Civilian Conservation Corps built the Eliot Tower in the 1930s, providing commanding views of Boston's skyline and harbor.