From Roughing It:
"During the afternoon we passed Sweetwater Creek, Independence Rock, Devil’s Gate and the Devil’s Gap. The latter were wild specimens of rugged scenery, and full of interest—we were in the heart of the Rocky Mountains, now. And we also passed by “Alkali” or “Soda Lake,” and we woke up to the fact that our journey had stretched a long way across the world when the driver said that the Mormons often came there from Great Salt Lake City to haul away saleratus. He said that a few days gone by they had shoveled up enough pure saleratus from the ground (it was a dry lake) to load two wagons, and that when they got these two wagons-loads of a drug that cost them nothing, to Salt Lake, they could sell it for twenty-five cents a pound."
See Burton 17th August. To the Valley of the Sweetwater: and Up the Sweetwater. 19th August
Horace Greeley:
But, one hundred and forty miles this side of Laramie, we leave the Platte, which here comes from the south, and strike nearly forty miles across a barren “divide” to its tributary, the Sweetwater, which we find just by Independence Rock, quite a landmark in this desolate region, with several low mountains of almost naked rock around it, having barely soil enough in their crevices to support a few dwarfish pines. Five miles above this is the Devil’s Gate—a passage of the Sweetwater, through a perpendicular cañon, some twenty-five feet wide, and said to be six hundred feet high—a passage which must have been cut while the rock was still clay. Here a large party of Mormons were caught by the snows, while on their way to Salt Lake, some years since, and compelled to encamp for the winter, so scantily provided that more than a hundred of them died of hunger and hardship before spring. Many more must have fallen victims had not a supply-train from Salt Lake reached them early in the season. And here is a fountain of cold water—the first that I had seen for more than a hundred miles, though there is another on the long stretch from the Platte to the Sweetwater, which is said to be good, but a drove of cattle were making quite too free with it when we passed. Here the weary crowds of emigrants to California were to gather yesterday for a celebration of the “glorious fourth,” and I was warmly invited to stop and participate, and I now heartily wish I had, since I find that all our haste was in vain.