What is the etymology for "the straight dope"?

If ever there was a question that the teeming millions should be able to handle, it’s this. What is the origin of the phrase “the straight dope”, meaning “the unvarnished truth”?

Early 19th century, according to web references like the Oxford English Dictionary.

From the Online Etymology Dictionary:

hmm…the two answers appear to be about a century apart.

I had presumed that “dope” had something to do with drugs, so the information about horse racing makes sense (although I didn’t realize that people were sophisticated enough to know how to drug horses for enhanced performance in 1901). Still, why does knowing which horse was drugged constitute the “straight” dope? If anything, crooked is a better word to connote dishonesty or cheating.

It didn’t. Dope by itself can mean inside information, such as which horse was drugged but it can also mean deceptive or fraudulent fast-talking. Examples from the OED include:

1904 W. H. Smith Promoters iii. 72 Unless you cover your dope with a sort of angel-of-light coating that would fool Gabriel himself, you’ll never get there.

1915 F. Froëst & G. Dilnot Crime Club xii, ‘Don’t pull any of that dope on me,’ said Coyne sharply.

1919 Detective Story Mag. XXVIII. i. 13, I suggested it to a detective, but he laughed at me and said the article was nothing but ‘dope’.

Straight has a long history of meaning non-evasive and frank as in straight talks. When you say, give me the straight dope, you’re saying, give me the real answers and don’t waste my time with foolishness you think I want to hear.

They weren’t, the horses were doped to reduce performance.

I think I saw where the word comes from the Dutch “doop”, meaning a sauce or gravy.

Dope is an old slang term for information. Straight is slang for truth.

the true information -> straight dope

I always had the impression it was the blunt truth. No feelings spared. Don’t ask for the straight dope if you can’t handle hearing the truth.

Mom, did daddy really die in a car crash? Well, do you want the straight dope? He ran off with two hookers and a bag of weed.

“You can’t HANDLE the Dope!!”

So whence “doping” in semiconductors? Is the sense that the silicon is adulterated, not pure, as the body is not “pure” when dope is ingested?

I posted this back in 2008 when it was asked previously.

Dope is also a product that is applied to fabric on aircraft to tighten, stiffen and weatherproof the fabric. I would assume when applying the dope you would want it to be “straight” or uncontaminated. The good stuff! Not a likely explanation since the stuff wasn’t invented until 1911.