I'm looking for locations in the USA that are high altitude and low humidity.?

The high desert of southeast California (Barstow, for example) and Arizona (Flagstaff) or New Mexico (Santa Fe).

For the US cities with the lowest annual humidity, eliminating those with a low elevation (under 3500):

4. EL PASO, TEXAS (Elevation: 3800 feet )—boasts abundant sunshine, very low relative humidity, scanty rainfall and relatively mild winters.

5. RENO, NEVADA (Elevation: 4498 feet)—abundant sunshine throughout the year. Here the daily range of temperatures often exceeds 45ºF. While afternoon temperatures may be above 90ºF, a light wrap is often needed after sunset. Rain occurs chiefly in the form of afternoon summer thunderstorms, but the humidity is very low during summer and moderately low during the winter.

6. ALBUQUERQUE, NEW MEXICO (Elevation: 4955 feet) —has an arid climate with abundant sunshine, low humidity, scant precipitation, a and wide, yet tolerable, seasonal range of temperatures.

7. WINSLOW, ARIZONA (Elevation: 4852 feet) — the seventh least humid city (46%) and eighth driest with annual precipitation totaling only 7.64 inches.

8. BISHOP, CALIFORNIA (Elevation: 4147 feet) — third or fourth driest city overall. Bishop has only 29 rainy days

High relativity humidity, yes; high absolute humidity no. As an example, during winter Fairbanks, Alaska often has ice fog when the temperature is 40 below (Fahrenheit or Celsius take your pick), which would correspond to close to 100% humidity. Despite the high relative humidity, the amount of moisture in the air is very small--during the summer the same amount of moisture might correspond to less than 1% relative humidity.

Denver, Colorado. It's a mile high and usually has zero humidity. The joke is, on a hot day in the summer, you can throw the water from a glass into the air, and nothing will come back down.