The oldest ground currently in the league?

[Eric the Half a Bee]

Is there a 19th century football ground in the league, playing 21st century football.
If not which is the oldest ground?

I would guess Deepdale as Preston have always played there since the league was formed in 1888. Bramall Lane another possibility.

[Cyclops]

I researched and wrote an article about Portsmouth's first football match in 1898 - a decade later than some clubs. But their beginnings were affected by somewhat odd circumstances:

"The pitch was shortly to be turfed and fenced and it was hoped that football could be played there after Christmas. However, the ground was covered with a crop of potatoes which the directors were 'anxious to sell'.

On 19 December 1898, the Hampshire Telegraph ran an advertisement inviting tenders for the building of two stands: the first, 100 feet long with seven rows of seats on the south side and the second, terracing which stretched for 240 feet on the opposite, north side."