Vandals smashed windows and daubed graffiti on heritage railway carriages, causing up to £30,000 of damage on the week of its 30th anniversary.
Paint was thrown on to an East Lancashire Railway (ELR) diesel engine and about 40 carriage windows were smashed in Bury between 20 and 25 July.
A 13-year-old boy and two girls aged 13 and 14 have been charged with criminal damage, Greater Manchester Police said.
ELR general manager Tracey Parkinson said it was "devastating" to see.
"It's really upsetting. It's been a week of mixed emotions for the railway, from celebrating our 30th anniversary and the dedication of our inspiring volunteers to cleaning up the aftermath.
"It is deeply saddening for me and the entire ELR family to see both our heritage and hard work destroyed," she said.
The ELR operates a 12-mile route between Heywood and Rawtenstall, using a range of preserved steam and diesel locomotives to haul vintage train services through the Irwell Valley.
It attracts about 200,000 visitors each year.