Born in Boston, Slade worked as a carpenter’s apprentice before becoming a civil engineer. He was elected city engineer of Boston in 1855, and served in that position for seven years. During his tenure, he oversaw the expansion of the city’s waterworks and authored several city plans that effectively map Boston’s physical expansion via a series of land reclamation projects during the mid-nineteenth century. Based on this experience, Slade later served as consulting engineer on city-sponsored waterworks projects in such cities as Hartford, Connecticut, Washington, D.C., Baltimore, Maryland, and Salem, Massachusetts.
Slade was essential in implementing the competition-winning plan for the Boston Public Garden (1859) by the Boston-based architect George Meacham. The Public Garden was created, along with the adjacent Back Bay neighborhood, with fill from other areas of the city. Working alongside city arborist John Galvin, Slade shaped the land to blend with nearby Beacon Hill, and arranged diverse tree plantings to create a naturalistic setting for visitors. Slade died in Roslindale, Massachusetts, at the age of 66.