The Spanish did not recognize the borders of the Louisiana Purchase and territories because they hadn’t been defined clearly yet. They sent soldiers to intercept the expedition a few times.
Here is one instance in 1804 when they missed the expedition, and returned to Santa Fe. The Spanish had instructions to keep the peace with the Pawnee no matter what. The Pawnee Chief would not let the Spanish pass, one account noted.
Also shown is the map of the Spanish Expeditions to intercept the Lewis & Clark. Mainly Lewis, because he did not have a current passport.