When looking at a border of this size, there are multiple factors to consider. I'll use the US-Mexico border as an example, since it's almost the same size as yours.
Today at the US-Mexico border, there no single, continuous barrier (see here). Only about 25% is covered by the fence. In between the sections of fencing are varying forms of sensors. In your world, these could be cameras, seismic sensors, physical guard towers, border checkpoints, or moving patrols.
Satellites would be impractical due to the number you would need to maintain a constant view of your border, but for the troop buildups along the border, like you describe. If US-191 is in our territory, it would become an equivalent to I-10(and US-90 east of Sierra Blanca, TX) on the US-Mexico, that is, a major artery for civilian traffic and border patrol. If not, then the same would apply to I-70, US-40, US-491, CO-90, and CO-141.
Depending on the military spending of the government, they would have Reapers and Global Hawks patrolling the border out of Peterson AFB(a decent choice, given it's on our side of the Rockies and the current home of NORAD)
A large section of the border is located in the center of the Rio Grande (see here). Parts of the Rio Grande are too fast moving to cross, so large parts of your border could be impassible due to geography. Of course this opens up opportunities for daring smuggler- or coyote-equivalents to try and find routes through (Hannibal and his freaking war elephants are a great example of the military using this tactic as well)