Hand Coloured Utah

Ever since May 10, 1869 the United States of America was joined from east to west by the railroad. It used to go around the Great Salt Lake in Utah. Then in 1904 they built a "bridge" across the lake from Ogden to Lucin, cutting off about 45 miles of the route and some dangerous grades and curves. It was replaced by a causeway in the '50's. I have 15 postcards that help us to remember this trestle.
Eight of the cards are of sunset or sunrise. There is a brilliant orange hue in the sky and a reflection of the light in the water. Three of them are basically the same picture of the same train with the same people with the same sunset at the same point on the track. However, each one is different because they each come from different publishers. Each publisher has put a change to the picture so that it is not violating the copyright, I guess. the titles on the fronts of the cards are different, too. One has a brass grommet in the right margin; one was mailed in 1939; the other two were not mailed.
I have the same situation with three other cards. This time the same train is on the same point on the trestle. One train has a bare puff of smoke, the second is starting to steam and the third is at full steam. But they are all just leaving the midlake station going toward the same hills. In one the clouds are wispy, in the next they are obvious and in the third they are pronounced. Also in the third, the caption at the bottom says it is sunrise not sunset - although the description on the back says sunset. Again, different publishers touching up the same picture to suit their needs.
My favourite postcard of the 15 is of a diesel engine heading east on the trestle toward the midlake station - there are two tracks on the trestle at this point - with a bag of salt from the Great Salt Lake attached to a metal grommet in the right hand margin. Guess what is missing from one of the other postcards!!
The other postcards of mostly of the midlake station or parts thereof. The train companies mentioned on the cards are the Western Pacific, the Southern Pacific and the Union Pacific.
There is one postcard that shows the train going through the salt beds of the Great Salt Lake. It shows a man behind a plow behind a mule working the salt beds. It is blank on the back and has not been mailed.
The oldest card that I can prove was mailed on January 7th at 4:30 p.m. in 1907.