Rhode Island's "hills" are glacial moraines and resistant bedrock remnants — modest by national standards but defining for the Ocean State's topography.
The original response contained inaccuracies: Jerimoth Hill is #1 (not Prospect Hill). Woonsocket Hill (~150 m) and Great Hill (~130 m) are lower. Yawgoog Hill (Boy Scout reservation) ~160 m.
Wisconsinan glaciation (20,000 BP) deposited terminal moraines (Charlestown, Jamestown) and sculpted resistant Essex Greenstone/Quartzite ridges. Post-glacial isostatic rebound continues (~1 mm/yr).
Highpointing: Jerimoth Hill = "drive-up" (short walk). Trail systems: Arcadia (Woolsey Hill), Big River (Escoheag), George Washington Management Area. Views: Limited by forest cover; fire towers (historically) provided panoramas.