Finding the key examples is easy, but getting the mainenance data will be a bit of an effort I suspect. The below all from a quick google:
For rail, I'd put the key "early" precedents as:
(obviously some kind of generic brick viaduct, available since the year dot)
1849 - (Brunel/GWR)
Royal Albert Bridge over the Tamar - long standing 15mph speed limit on it (because of severe approach curves i think though)
1859- (Brunel/Cornwall Rly)
Timber "fan" viaduct [Book -"Brunel's Cornish Viaducts".
Link to site which gives timings between stations on the line]
1890-(North British Rly) Forth Bridge [Mainenance costs given
here]
>1870/50 - Meldon /Crumlin Viaducts (
Photo,
Photo) Steel Warren Truss designs.[
Link refers to weight carried,
slight mention of maintenance, on the latter (earlier).
Suggest asking at uk.railway newsgroup is the best way to find people with the right books for speed limits, weight limits, and maintenance if we're lucky.
Would also suggest the dates which designs were first built is more to do with when they were needed than when the technology was available. I mean, they only built the Forth Bg because of the Tay Bg collapse - it's more about circumstance. I think we should be generous when permitting bridge types by date.
for Canals:
1796 - Longdon on Tern Aquaduct (
Pics)
1805 - Pontcysyllte Aqueduct (
Wikipedia has construction cost but not mainenance. Load /speed not an issue given all that water...)