Webster's Revised Unabridged Dictionary · 1913

Upon

Upon , preposition

[Anglo-Saxon uppan, uppon; upp up + on, an, on. See Up, and On.]

On; -- used in all the senses of that word, with which it is interchangeable.
Upon an hill of flowers. — Chaucer
Our host upon his stirrups stood anon. — Chaucer
Thou shalt take of the blood that is upon the altar. — Ex. xxix. 21
The Philistines be upon thee, Samson. — Judg. xvi. 9
As I did stand my watch upon the hill. — Shakespeare
He made a great difference between people that did rebel upon wantonness, and them that did rebel upon want. — Bacon
This advantage we lost upon the invention of firearms. — Addison
Upon the whole, it will be necessary to avoid that perpetual repetition of the same epithets which we find in Homer. — Pope
He had abandoned the frontiers, retiring upon Glasgow. — Sir. W. Scott
Philip swore upon the Evangelists to abstain from aggression in my absence. — Landor

Upon conveys a more distinct notion that on carries with it of something that literally or metaphorically bears or supports. It is less employed than it used to be, on having for the most part taken its place. Some expressions formed with it belong only to old style; as, upon pity they were taken away; that is, in consequence of pity: upon the rate of thirty thousand; that is, amounting to the rate: to die upon the hand; that is, by means of the hand: he had a garment upon; that is, upon himself: the time is coming fast upon; that is, upon the present time. By the omission of its object, upon acquires an adverbial sense, as in the last two examples.

Collocations (3)
To assure upon (Law) , to promise; to undertake.
To come upon , See under Come.
To take upon , to assume.