Shannon family in Kingscourt

Hello,

I am trying to find out information about my great-great-grandmother, Margaret Shannon, who came over to New Orleans at age 15 with her sister Jane around 1845. She married Owen Duggan in 1853 in New Orleans where their two eldest sons were born. She was baptised at the same time as the two sons into the Catholic faith. One version of their journey is she and her sister passed to Elllis Ilsand and then they were routed southward to Louisiana (New Orleans). Margaret had seven siblings: Jane, Susan, Sarah, Eliza, Robert, Mary (b. 1840 and reunited with Mary after 50 years), and Frank. Five of the siblings, Susan, Sarah, Eliza, Robert, and Frank, remained in Kingscourt County Cavan. 

I would like to learn more about Margeret, her father who I believe was John Shannon, and especially about her mother's lineage, who I believe was Martha Davinson Shannon. 

Thank you for any help you might be able to provide.

Tamra J. (Case) Higgins

Vermont, USA