[2] It was improved with trails,[3] picnic areas, fences and other amenities and generally well maintained through the first half of the 20th century.

[5] In 2021, the main park entrance from Totten Pond Road was temporarily closed as construction began on a capital improvement project to add "a water spray park, children’s playground area, picnic area, pavilion, multipurpose half court and a gaga pit".

[2] Due to the topography of Big Prospect, a very unusual configuration existed, with the novice area above a much steeper expert slope.

The former headquarters of the Polaroid Corporation was located adjacent to the southwest corner of Prospect Hill Park.

[8] The site was vacant for many years, until construction began in 2013 of "1265 Main," a mixed use retail and office project.

Beginning in 1951, the United States Air Force utilized Big Prospect for research purposes.

Projects included Experimental SAGE Subsector in the 1950s and the Joint Tactical Information Distribution System in the 1970s.

In 1997, the Air Force left Prospect Hill Park, and in 2002 all radio equipment was relocated to Big Prospect, serving Waltham's fire, police, public works, parks and recreation departments, the Massachusetts Army National Guard, the Civil Air Patrol, and the Waltham Amateur Radio Association.