How tall does land have to be a mountain?

Answer 1

"Geographers, on the other hand, who's

primary interests often concern topographic anomalies like mountains

and basins, usually reserve the term 'mountain' for a positive

topographic feature which rises to a height of at least 305 meters

above the surrounding terrain. Anything less than 305 meters in

height is considered a hill, and anything considerably less than 305

meters is termed a 'hillock.' "

http://www.newton.dep.anl.gov/askasci/env99/env261.htm

EDIT: 305m = 1000ft

Answer 2

A mountain is typically defined as a landform that rises at least 1,000 feet (300 meters) above its surrounding area. This can vary based on local geography and definitions.