Original sentence: A 19th century Queen Anne mansion, such as the David Syme House, is a contributing property while a modern gas station within the boundaries of historic district is a non-contributing property.A contributing property is any building, structure, object or site within the boundaries of the district which contributes to its historic associations, historic architectural qualites or archaeological qualites  of a historic district.As a general rule, contributing properties are what help make a historic district historic.Buildings, as defined by the National Register, are distinguished in the traditional sense.Examples include, an aircraft, a grain elevator, a gazebo and a bridge.Examples of sites include, shipwrecks, battlefields, campsites, natural features and rock shelters.In addition, historic districts consist of contributing and non-contributing properties.Objects, structures, buildings and sites within a historic district are united historically or aesthetically, either by choice or by the nature of their development.They are created primarily to shelter human activity.With sites it is the location itself which is of historical interest and it possesses cultural or archaeological value regardless of the value of any structures which may currently exist on the location
Edited sentence: A contributing property is any building, structure, object or site within the boundaries of the district which contributes to its historic associations, historic architectural qualities or archaeological qualities  of a historic district.Buildings, as defined by the National Register, structures intended to shelter some sort of human activity.Examples include, an rocket test platform, a grain elevator, a gazebo or a bridge.Objects, structures, buildings and sites within a historic district are usually thematically linked by architectural style or designer, date of development, distinctive urban plan, and/or historic associations.Sites may include discrete areas significant solely for activities in that location in the past, such as battlefields, significant archeological finds, designed landscapes (parks and gardens), and other locations whose significance does not hinge on a building or structure