I would like to know if it is possible to buy milk without supporting
the inhumane treatment of calves.  Horizon Organic touts its 'happy
cows' but all I could find on their website about what happens to
their male calves is that they're 'sold to be raised as beef'.  Not
sure if that means veal, and if so, it's not clear how the veal is
raised.  Are there dairies in the US that do not sell the male calves
born to their milk cows to be raised as veal?  Or, are there dairies
that sell calves exclusively to veal farmers who do not raise the
calves in tiny stalls?

The dairy section of my favorite health-food store carries a product
labeled as "cruelty-free milk." You might want to look for milk that
bears such a label.

that's a good question.

personally, for a long time I pursued this line of reasoning, then
came to the conclusion one day that while keeping an animal in a
cruelty-free environment is a vast improvement over the widely
practiced alternative, killing them in the end is still cruel. I know
this is just opinion; I hope an answer to your specific question will
be forthcoming; I've tried to find it myself but finally filed it into
the mind-folder called 'Best Kept Secrets'.

I like this site:  http://www.theanimalspirit.com/vegan.html

Few Americans eat veal, even baby beef is rare, but it may be an
important export. Typically the milk farmer is not concerned what the
buyer does with the male calves. It would be rare that the milk farmer
kept the male calves more than a few weeks, but they might be raised
by a subsidiary, which would allow the disposal to be known with
reasonable certainty. At what age is a male calf considered too old to
produce veal?   Neil

Here's one for you:

http://www.organicpastures.com/

Located in Fresno, Ca, owner Mark McAfee sez:
"We do not sell our calves to the veal market. I am morally against it and my
wife would object, she loves babies.... Our bull calves are sold to be
raised organicallly on pasture and used for beef when they are huge
(about 2 years old or 1600 pounds)."

They also haul their milking machines out to the pasture; see website.
 Interesting concept.