Why does the horse "think it queer" in "Stopping By Woods on a Snowy Evening"?

I am not sure exactly how intelligent horses are, but like many domesticated animals, they are creatures of routine. So, in Frost's "Stopping by Woods on a Snowy Evening," the horse finds it unusual to stop at that particular place, "without a farmhouse near/ Between the woods and frozen lake" (lines 6-7) because this is not the narrator's routine with his horse. The horse is accustomed to a destination such as a farm. The horse may also be accustomed to stopping at the lake for some water. This narrator is stopping in the middle of nowhere, from the horse's perspective. It is also a snowy evening, and while the horse is probably not suffering in this weather, stopping like this on a cold night might also be unusual. One gets the impression that the narrator does not often give in to the impulse to stop for a quiet, contemplative moment. Thus, this is outside of the horse's normal routine and he thinks it odd.

Where has the poet stopped in "Stopping by Woods on a Snowy Evening" and why does his horse find it strange?

Robert Frost wrote this poem, along with many other of his most famous compositions, at his house in southern Vermont. The house sat on seven acres of wooded land, and Frost himself apparently spent many hours in the woods in this area. It seems entirely possible, then, that narrator of this poem is, in fact, describing woods very similar to those near Frost's home at the time of his writing. They are beautiful and tranquil, quiet and dark, and the narrator obviously enjoys watching the snow fall in them, in the same way Frost would have enjoyed the areas surrounding his home. The narrator's horse shakes his bells "To ask if there is some mistake" because this narrator does not, evidently, stop like this very often. He has stopped "without a farmhouse near," which must be uncommon for the pair, and so the narrator assumes that his "little horse must think it queer."

The narrator of the poem has stopped in the woods to watch them "fill up with snow" (line 4), the woods of someone who lives the village, a moment of quiet contemplation and beauty, I would say.  The horse is puzzled because horses are creatures of habit, and this horse is likely to not be accustomed to stopping in the middle of nowhere. The narrator says the horse thinks it queer "To stop without a farmhouse near" (line 6), suggesting that the horse is accustomed to a route in which stops are made where there are houses, not in the middle of the woods. The horse probably expects a stop to include water and hay and perhaps being put in the barn for the night. The horse has a moment of impatience, shaking his harness bells, "To ask if there is some mistake" (line 10).  This seems to bring the narrator out of his moment of absorption, reminding him he must move on, since he has "promises to keep,/And miles to go before I sleep" (lines 14-15).    

What seems strange to the horse in "Stopping by Woods on a Snowy Evening"?

Robert Frost has been quoted as saying:

Everything written is as good as it is dramatic. It need not declare itself in form, but it is drama or nothing.

This explains a lot about his poetry. In "Stopping by Woods on a Snowy Evening" he is describing the kind of snowy scene that often appears on Christmas cards. It is silent, peaceful, and beautiful, like the song "Silent Night." Yet Frost intentionally makes the poem dramatic by injecting a note of mystery. Why is he stopping here? First he thinks about the man whose woods he has stopped to admire.

Whose woods these are I think I know.
His house is in the village, though;
He will not see me stopping here
To watch his woods fill up with snow.

Why should the poet be concerned about being seen sitting there in his sleigh looking at the man's trees?

Then the poet's horse seems to be reprimanding him for stopping here on a cold, dark night. Even a dumb animal knows he should be heading for home, where there is shelter and warmth for both man and animal.

My little horse must think it queer
To stop without a farmhouse near
Between the woods and frozen lake
The darkest evening of the year.

The horse is thoroughly familiar with this route. They have been over it back and forth countless times. The poet has evidently driven into the village to pick up supplies and do some last-minute Christmas shopping. He often stops at farm houses along the way just to say hello to friends, warm his hands at their fireplace, have a drink, and perhaps to ask if they need anything in the village. What bothers the horse is that there is no farmhouse nearby. So why are they stopping?

The poet cannot explain either to the owner of the woods or to his horse that he is stopping because of the striking beauty of the sight of the trees being covered with the slowly drifting snow. Since this is late December, the deciduous trees in New Hampshire, where the poem is set, would all be bare. The poet must be stopping to look at fir trees. Their stiff, horizontal evergreen branches easily catch the falling snowflakes, and they quickly turn a dazzling white.

The poet is concerned about the owner of these woods seeing him sitting here because he knows the owner would not understand that he is simply admiring their beauty. Fir trees are grown for sale as Christmas trees all over New Hampshire. But the rural residents, like the poet, do not buy their trees off lots in town. They just go out and cut down a sapling. That is what the owner would suspect the poet of contemplating. Maybe--as a matter of fact--the poet does have that in the back of his mind. It is just a couple of days until Christmas and he doesn't have a tree.

His horse breaks the spell by jingling his harness-bells. The poet is reminded that he still has a long way to go before he can get warm and go to sleep. He has responsibilities, including a responsibility to this little horse. He cannot continue sitting there meditating--but perhaps he has taken as much out of the beautiful scene as he was able to take. The experience results in one of Robert Frost's most popular poems.