If your kin were hitched in Arizona, Idaho or Nevada you are really, really in luck, and if they tied the knot in California, western Colorado, Montana, Oregon, Utah, eastern Washington, New Mexico or Wyoming you are just plain in luck. If they ran off to Alaska to get married you are out of luck, unless you are descended from one of the 33 couples whose records are included in the Western States Marriage Record Index.
As of today, September 29, 2013, the WSMRI contains 911,439 early marriage records for the western states and most of the pre-1900 marriages for Arizona, Idaho, and Nevada are included. Other states are not as complete, but this is an ongoing project with records added every year. Thanks to the efforts of volunteers at BYU-I Arthur Porter Special Collections area of the David O. McKay Library in Rexburg, Idaho, we have this amazing index, which should be one of the first places you look for a western states marriage record. They scour the west for any kind of marriage record collection and add it to the index.
If you don’t know exactly where your ancestors got married, this is an especially helpful resource, as you can search all the western states at once. It also helps in cases where they traveled across a state line to marry.
If you get no search results, click on “Search Tips” for some pointers. Also, check to see if your county and years are included in the index by clicking on “List of Counties by State”.
You will get a nice list which also has a link to “Microform Availability”. This will take you to the FamilySearch Catalog where you can see exactly where the records were extracted from, in case you want to view the record for possible additional information.
Another feature I like is the link to Utah pre-1887 sources. The indexers have identified many records which contain early marriages, such as church and court records, and have listed them for easy reference. So considerate.
The Western States Marriage Index is only one of many helpful resources offered by BYU-I Special Collections and Family History. I may highlight more in the future, but take a minute to check out what they have. It could be your lucky day.
On Granny's Trail 
Thanks, Amy. Sounds like you have had some good luck with the index, and it is coming in handy to make your case on Family Tree. I wonder if the person who made the change will let it be or will keep trying to change it. Funny how determined some folks can be even when faced with pretty solid evidence!
Just this morning I got my weekly update from FamilySearch for entries I’m “watching” and saw that someone had removed a second marriage for one of my great-great uncles that I’d added to Family Tree from the Western States Marriage Index. (Two very distinctive names, and the ages are right, and I’ve checked that there’s no chance that I have the wrong people.)
Someone deleted the relationship and wrote, “A— H— never married this individual.”
So I restored the relationship and explained in much greater detail about the source for the marriage and that the marriage was probably short-lived since it wasn’t mentioned in an autobiography this uncle wrote.
Anyway, the Western States Marriage Index is a great source, and this is a great write-up, Dayna. Thanks!