The first Inter-City railway.

[RyanOPlasty]

Liverpool to Manchester (1830) is widely regarded as the world's first Inter-City railway. Neither Liverpool (1880) nor Manchester (1853) was a city at the time, so IMHO it doesn't qualify.

What was the first railway between two places which had city status at the time of opening?

I think it may be the Newcastle and Carlisle Railway (1837)

 

[The Pelican]

If you wanted "First railway for which trains running just from one end to the other end with no extensions were counted as InterCity by BR", then the London and Birmingham in 1838 would be the obvious one. I think the liverpool and manchester is the right choice though, as the InterCity classification has always been based more on a notional equation of 'population times distance" than city status.

 

[RyanOPlasty]

If you wanted "First railway for which trains running just from one end to the other end with no extensions were counted as InterCity by BR", then the London and Birmingham in 1838 would be the obvious one. I think the liverpool and manchester is the right choice though, as the InterCity classification has always been based more on a notional equation of 'population times distance" than city status.

Birmingham didn't achieve city status until 1889, but Coventry was on the route. London-Coventry is between two cities, but 1 year later than Newcastle-Carlisle

 

[A S Leib]

I know that a lot of countries don't have distinctions between towns and cities, but outside the UK, was anything earlier than Berlin – Hamburg? That opened in 1846 and both cities had the 100,000+ populations of a Großstadt in 1849.

 

[Port Road]

May 5th, 1835; Brussels - mechelen?