Your posting caught my eye because of location. Don't know if I'll be much help but I only recently found out who my maternal great-great-grandparents were via my gg-gf's Civil War pension. Am brand new to this surname so not sure of spelling variations, i.e. "Glennon" vs "Glennan" at this point.
My gg-grandparents were Thomas J. McElwain (born about 1828 in Randolph, Vermont) and Maria A. Glennan (born May 1832 NY). That's what her name looks like on copy of marriage cert contained in the pension. They were married in July 1852 at St. Bridget's Church, Avenue B, Corner of Eighth Street in NYC.
Thomas J. McElwain died in March 1863 in NYC from illness contracted while a soldier in the Civil War.It gives the names & birthdates of their 2 small children:
1) Thomas Francis McElwain (b. 21 Dec 1857, died sometime between April 1863 and 1900 census) Know nothing else about him at this point.
2) Agnes G. McElwain - my gg-grandmother - (born 23 January 1860, died sometime after 1910 census, around 1930-ish per my Mom). She was married to James J. Flynn.
(Suspect Agnes' middle initial may stand for "Glennan" and her mother Maria's middle initial may stand for "Agnes.")
Maria A. [Glennan] McElwain stayed in NYC after her husband's death and is listed on early tax rolls (1869 NYC) as a widow and dressmaker.
By 1900 Maria was living with her daughter, Agnes G. [McElwain] Flynn and son-in-law James Flynn in Brooklyn, NY and was still living with them on 1910 census, very near to the Queens border.
So - at this point, I know nothing about our Glennans but perhaps one of the surnames above may ring a bell with your father.
By the way, FYI, I was born in Brooklyn, NY in 1950, so I suspect I may be close to your parent's gen.
Let me know if anything rings a bell and I will contact you as I dig further into our Glennan line, i.e. if I can discover who Maria's parents or siblings were. Just so you know they were in NY quite early - at least by May 1832 when my gg-grandmother was born.