The slough was excavated through what used to be the Montlake Landfill. Formerly the Ravenna Landfill, it was used by the city of Seattle for residential and industrial solid waste from 1926 to 1966. It was closed five years later and overlaid with two feet of clean soil. Some of the land has been built upon by the University; the rest consists of fields, marsh, wetlands, and the college's main parking lot.
Before the lowering of Lake Washington during the early part of the 20th century, Ravenna Creek flowed into marshland north of where University Slough now terminates, and the land through which the slough would be cut lay under the waters of Union Bay. Construction is due to begin in 2004 on a project that would reconnect Ravenna Creek to Union Bay by piping it underground to University Slough, thus converting it from a stagnant drainage channel to the outfall for one of Seattle's urban creeks.