Hi Katelyn,
Thank you for your message. I hope that someone with information makes a connection with you and helps you to further your research.
In the meantime, it will greatly help help if you can narrow down the place of origin further to a parish.
I did a search for the surname Glackin in the Tithe Applotment Books. These are land records taken 1823-38. There was only 10 results-are any of these names familiar?
http://titheapplotmentbooks.nationalarchives.ie/search/tab/results.jsp?surname=Glackin&firstname=&county=Donegal&parish=&townland=&search=Search
The later land record called Griffith?s Valuation (1848-64) recorded 7:
http://www.askaboutireland.ie/griffith-valuation/index.xml?action=doNameSearch&Submit.x=55&Submit.y=3&Submit=Submit&familyname=glackin&firstname=First+Name&baronyname=&countyname=DONEGAL&unionname=&parishname=
Here is a list of all the townlands in Donegal matched with the Electoral District that they belong to.
http://freepages.genealogy.rootsweb.ancestry.com/~donegal/dedx.htm
Perhaps you can use this list to help narrow down the parishes further according to Electoral District they belong to. By the way, I think that you are looking for the Cloghan district as opposed to Claghan.
Remember to post as much information as you can with regard to the people you are researching. The more information you post, the more likely it is that one of our volunteers will be able to advise or assist you. Also include information concerning which sources you may have already used so others may further your search.
Kind regards,
Genealogy Suppot