If you know what religious denomination they were, you may also want to check the catalog page on familysearch.org. https://www.familysearch.org/search/catalog/search/
Type in Bennington, Wyoming and it should come up. You have to register an account to view any records but it's all free.
Under church records in Bennington, the only denomination they have records for is the catholic church going back to 1872. I looked through the marriages and it looks like there was what looks like Anna Todt married to a Charles in 1880, but it's hard to read (image 114 of 168 on the bottom left).
If they were catholic, they may have gotten married in one of the (relatively) bigger towns nearby like Attica or Warsaw. I also know that the catholic churches in larger towns in this area had 'missions' in smaller towns instead of the smaller towns having their own parish, so the records for that town may be included under the records for one town, but actually took place somewhere else.
Any marriage records before the mid-late 1880s in New York were not registered with the state and will not be in the marriage index, so the best route will probably be finding the church marriage record. Individual towns may have kept their own civil records, but you would have to ask the individual town clerk about that, and sometimes they may not even know.
I hope this helps.