First time it's ever been tried.
4 seconds sound clip from the The Big Trail (1930) movie soundboard.
You can hear this line at 00:04:19 in the Blu-ray version of the movie.
Quote context
[...]
- Well, surely there's fur aplenty out in that land beyond Oregon.
- Plenty.
- But I gotta kill me a pair of skunks, back apiece on the road to Santa Fe.
- Hey, wait, wait. Friend, how do you find that valley?
- Wellmore here is sending a bull train clear through to old Tom Williams's trading post.
- First time it's ever been tried.
- String along behind them and, if they make it through, you'll find your valley.
- And tell that great white mountain hello for me.
- Hey, maybe he fed us a fairy tale.
[...]