Colorado State Highway 121
|Maintained by CDOT|
|Length:||30.425 mi (48.964 km)|
|South end:||Waterton Road near Littleton|
| US 6 in Lakewood
US 40 / I‑70 Bus. in Lakewood
I‑70 / I‑76 in Arvada
US 36 in Broomfield
|North end:||US 287 in Broomfield|
The route, also known as Wadsworth Boulevard, Wadsworth Bypass, and Wadsworth Parkway, starts at a junction with Waterton Road in unincorporated Jefferson County (near Littleton) and ends at the junction of U.S. Route 36, U.S. Route 287, and State Highway 128 in Broomfield. State Highway 121 passes through portions of southwest Denver County.
The name Wadsworth comes from Benjamin Franklin Wadsworth, one of the founders and first postmaster of Arvada. In northwest Arvada, Wadsworth Boulevard passes over Hackberry Hill at the site where a landmark hackberry tree, for which the hill was named, stood before it was cut down to make room for the highway in 1937. 
|Jefferson||0.00||0.00||Waterton Road||Southern terminus|
|Lakewood||7.49||12.05||US 285 (Hampden Avenue)||Interchange|
|9.06||14.58||SH 8 west (Morrison Road)||Eastern terminus of SH 8|
|12.44||20.02||US 6 (Sixth Avenue)||Interchange|
|13.59||21.87||US 40 / I‑70 Bus. (Colfax Avenue)|
|Arvada||16.79||27.02||I‑70 / I‑76 east – Denver, Fort Morgan, Grand Junction||Exit 269A on I-70; exit 1A on I-76|
|City and County of Broomfield||25.82||41.55||SH 128 west (Interlocken Loop)|
|26.02||41.88||US 36 – Denver, Boulder||Interchange|
|26.42||42.52||US 287||Interchange; northern terminus|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi
- "Segment list for SH 121". Retrieved 2007-05-12.
- "Jefferson County, Colorado Place Names Directory". Retrieved 2012-03-23.