Elevation refers to how far above sea level something is, like a city. Every city has different elevations at various locations within its borders. When determining elevation, you can look for a specific elevation at a prominent point, you can find multiple elevations and come up with an average, or you can get the highest and lowest points within a city. Knowing the elevation of a city will give you an idea of the terrain, or -- in the case of high elevations -- if it may be hard to breathe there due to the reduced oxygen.
Look at a topographic map for the city. A topographic map contains elevations and will show you subtle differences in elevation throughout the city. For specific elevations, the United States Geological Survey's National Elevation Dataset is an available resource. The zoning and planning departments of many cities will also have topographic maps.
Check out the city’s information in an atlas. An atlas contains a lot of the same information as a topographic map, but will usually give average elevations as opposed to many elevations for specific areas.
Utilize online resources, such Earth Tools or Google Earth, to look up the elevation of the city. Type in a specific address or location within the city for an exact elevation. For a more general elevation of the city, view a topographic map or use multiple addresses throughout the city to get an average.