Black Hawk is about 65 kilometres west of Denver via Interstate 70 and Colorado Highway 119 through Gilpin County, or via the more scenic Highway 6 up Clear Creek Canyon from Golden. The drive takes around an hour from Denver in normal conditions, longer in winter. All the major casinos run free shuttle buses from various Denver-area pickup points — check individual casino websites for schedules, as this is the most practical option if you don't want to drive mountain roads.
There is no public transit connection. A car is effectively required unless you use the casino shuttles.