The 1865 Massachusetts State Census is now online and available for browsing.
http://pilot.familysearch.org/recordsearch/start.html#p=0If you are looking just for Irish, it is a little easier to go page by page as you can look in the birthplace column first and go through a page fast. You do have to wait for each page to load and that is a little tedious. I am working my way through Leominster looking for my great grandmother and other relatives but I'd like to tackle Worcester looking for relatives as well.
You have to go page by page. Worcester is separated into wards. Can anyone tell me what wards that the Irish were concentrated in in 1865?