This topographic map was produced by the United States Geological Survey and illustrates the community of Northeast, Maryland which is located along the shoreline of Chesapeake Bay. Topographic maps show elevations of the land's surface (in feet above sea level) through the use of contour lines. The brown lines on this map are contour lines. They trace points of equal elevation across the map. For example the brown line with the "30" label in the left central portion of this map traces points that are 30 feet above sea level across the landscape.
Let's consider the position of the 30 foot contour line with the shoreline of Chesapeake Bay. The elevation of Chesapeake Bay is considered to be sea level, or zero feet. Note that there are two brown lines between the "30" line and the Bay's shoreline. The brown line closest to the bay traces points that are ten feet above sea level and the second brown line traces points that are 20 feet above sea level. With lots of practice, experienced users of topographic maps can quickly "read" the landscape and realize where moutains, ridges and valleys are located.
Topographic maps show many other important features such as highways, streets, buildings, railroads, political boundaries, certain land use types and much more. This topographic map was obtained from MapCard, an online service that provides subscribers access to USGS topographic maps for all 50 states and aerial photo coverage for most of the US.