North of Monument at County Line Road, I-25 rises up and crests Monument Hill, sometimes refered to as the Palmer Divide. At an elevation of 7352 feet, it is prone to severe winter weather. As a result, CDOT has continuous lighting along a three or so mile stretch of it, very rare in a rural area. At first I didn't know what the lighting was for, but Mike Ramsey dropped me a line clearing things up. I-25 passes to the west of the main part of town, but the town has spread out to envelop both sides of the freeway.
Castle rock is also where the pressure of traffic from metro Denver starts to be felt.
It has been an accident-prone stretch. This section of I-25 was meant to handle 45,000 VPD, and was actually carrying 60,000 VPD in the late '90s. CDOT decided to upgrade the section by adding a third lane in each direction. Phase II will be the segment from Castle Pines to Founders in Castle Rock. At Lincoln Avenue, I-25 enters the more developed portion of metro Denver.