I’ve lived in Louisville for all of my 34 years and I’ve attended the Derby probably a dozen times. Here’s my two cents:

I agree that if you are doing the Infield then you should just dress comfortably, wear sunscreen and try to not drink yourself into the hospital.

For the grandstands there is no ‘required dress’ but the local logic is that the closer you are to the center of the grandstands, the nicer you should dress. Derby tickets aren’t cheap and it seems pretty silly to pay all that money and not get the full experience. And the dress is part of the experience. We have seats every year on the far end of the grandstands. In that section it’s a mixed bag. I see people in shorts and polos and people in three-piece suits. As you get closer to the center where all the owners are, most men wear a suit or a blazer and tie.

As a Southern man I prefer the blazer and contrasting pants to a suit most of the time. One thing about Derby is that ‘loud’ or extremely colorful blazers are encouraged. I have one searsucker and one madras plaid blazer that I rotate for the Derby and that’s pretty much the only thing I wear them to (the searsucker is appropriate for church in the spring). Also, loud ties are a regular sight, usually with a horse/racing theme. Hats are becoming more common among the men. Mostly straw fedoras that aren’t too hot (the weather for Derby can range from the 40′s to high 80′s depending on the year).

All of the comments about being unique, etc are pretty silly IMO. For the Kentucky Derby the dress is a big part of the experience. Stand there in a good outfit, sing My Old Kentucky Home with 200,000 other people and tell me it’s not a moving experience. We’ve had friends in town for the Derby many times and they all say they are glad they went for the more formal attire. It’s sort of like if I ran with bulls in Spain I would wear the typical garb for that. You’ve got 364 other days to be ‘unique’. But respecting tradition is about being a part of something…not deliberately ignoring it.