Concept in Definition ABC

Relevant event or event taken as a reference

The concept of milestone is used in our language especially to refer to that relevant, notable event or event, and that as such will be erected as a point of reference and almost always as a consequence of that tremendous influence that marks a before and after in the context in which it occurs.
"The appearance of Internet It is a milestone in the field of technology ”.
"The female vote was a milestone in the history of social conquests by women."

Signposting on routes and roads to indicate distances, directions and mark borders

On the other hand, the word is used to designate that post, generally made of stone although it can be made of any other material, found at the behest of roads or routes and borders to indicate a direction, a distance or the limits of a territory.
We must emphasize that it is very common for the landmark to consist of small or medium-sized sculptures.

Kilometric milestone: indicates kilometers and routes through which it is traveled

In the case of signaling distances on a road or route, the so-called kilometer milestone stands out. It consists of a typical traffic signal which will indicate the distance between the beginning and the end of a route and whose fundamental mission is to guide the travelers who travel it.
Kilometer milestones are metal and extremely useful for those who travel along the routes because they appear regularly on the road, that is, every certain distances, and they inform us the kilometer through which we are going, plus, in some cases, the number of the highway through which we are circulating.

That is, this sense of the word is used as a synonym for signal. The milestone is a sign.

National Historic Landmark: building, work, element that has a historical mark

And in the United States the word has a special use in the blueprints historical and cultural since a national historical landmark will be that building, structure, locality, object, that the government national recognizes it as such due to its historical imprint.
All of these are listed and made official in a record which is known as the National Register of Historic Places. Of course, as such they should enjoy a I respect and preservation by the federal state if they are at risk of suffering an affront.