MP: .06
Location: I-5 and Maytown Rd SE, Maytown
Junction I-5 and Maytown Rd, the beginning of SR 121
MP: 2.52
Location: Maytown Rd SE and Tilley Rd S, Maytown
SR 121 turns left onto Tilley Rd S with little signage. It heads to Millersylvania State Park
MP: 7.51
Location : I-5 and 93rd Ave SW, Tumwater
SR 121 goes by the state park and turns onto 93rd Ave SW without signage. It ends at I-5 just south of Tumwater
