| State: | CO |
| Type: | SH |
| Route: | 121 |
| Map: | Colorado State Highway 121 Map.svg |
| Map Notes: | Map of north central Colorado with SH 121 highlighted in red |
| Length Mi: | 30.425 |
| Length Round: | 3 |
| Length Ref: | [1] |
| Direction A: | South |
| Terminus A: | Lockheed Martin Space Systems near Roxborough Park |
| Junction: |
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| Direction B: | North |
| Terminus B: | in Broomfield |
| Counties: | Jefferson, Denver, Broomfield |
| Previous Type: | SH |
| Previous Route: | 120 |
| Next Type: | SH |
| Next Route: | 125 |
State Highway 121 (SH 121) is a 30.425 mile (48.96 km) long state highway in the U.S. state of Colorado. SH 121's southern terminus is at Waterton Road near Littleton, and the northern terminus is at U.S. Route 287 (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 at the entrance to the main plant of Lockheed Martin Space Systems) and ends at the junction of U.S. Route 36, U.S. Route 287, and State Highway 128 in Broomfield at a trumpet interchange. 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. [2]