This first line gives us some straight forward action. We've got a jar, a speaker, and a setting (Tennessee).
This jar may even be a particular, popular jar, the Dominion Wide Mouth Special, which was all the rage, or at least as much of a rage as fruit jars can be, around the time that this poem was written.
The particular jar doesn't matter so much, though, as the general idea of a jar as something man-made and ordinary.
Also, don't forget the other meaning of the word "jar"—something sudden and unpleasant. When you're riding in a car, and the driver brakes out of the blue, you could call it "jarring." We wonder if this jar is going to… jar anything in the poem to come.
And round it was, upon a hill.
This line gives us more detail about both the jar and where it was placed. The jar is round, which is no big surprise. It's emphasized that this is just a run-of-the-mill jar.
The jar isn't just placed in Tennessee, but on a hill in Tennessee. When we think hill, we think round. Hills are soft, much rounder and calmer than jagged mountains. We can imagine this jar, sitting perfectly on the crest of a little hill.
Though this jar is an outsider, placed by a human on this hill, already we can see it as the king of its little territory, looking down upon everything around it.
It made the slovenly wilderness Surround that hill.
Interesting. Now, the jar is affecting the world around it. Apparently, there's a lot of wilderness around the place where the jar is. This wilderness is slovenly, or unclean, unmaintained—probably messier than your bedroom at its worst.
You'd think that this wilderness, described as so beyond control, would be unaffected by something like a jar. Yet this jar "made" the wilderness surround the hill upon which it rested. Saying that a jar "made" wilderness do something is an example of personification on two counts. Personification is when an object, or anything inhuman, is granted human attributes or abilities. Thus, saying that the jar can make something do anything—or that wilderness can obey orders—is personification.
Beyond considering the personification present in these lines, we've also got to think about points of view. Don't forget the "I" in line 1. It's possible that this wilderness is being made to surround the hill only for the perspective of this "I," the speaker. His eye is so drawn to the jar, which he placed on the hill, that all of nature seems to surround the jar upon its orders.
Also, pay attention to the sounds going on in this poem. Now, we've got the sound of the word "round" and "hill" twice in four lines. This repetition makes the poem sound enclosed and static (not moving), just like the jar. Even the word "wilderness" stays within the given sounds, because the first syllable (wil) echoes "hill." (For more on this, check out our "Form and Meter" and "Sound Check" sections.) Even the poem's sound gives a condensed, closed-off impression.