Unfortunately the letter and the envelope it was mailed in became have become separated in the past making it impossible to identify the author of this letter who signed it only as “your affectionate son, Henry.”
Because it was written on “Pennsylvania” patriotic stationery and given that he author mentions Company H in the letter, my assumption is that he served in that company in a Pennsylvania Infantry regiment but I have not been able to identify the regiment that was posted at Seneca Mills, Maryland, on that date.
Perhaps a Spared & Shared reader will be able to figure it out and let me know. We know his parents were living, that he had a brother named Al, and probably some sisters.
Transcription
Seneca Mills [Maryland]
Camp Seneca
November 18, 1861
Dear Mother,
Your letter dated the 13th was duly received and I was glad to hear from you. Today our new uniforms come and Co. H goes on picket duty to the river. It is very cold here and we will move this week to Washington.
In regard to my spending so much money at the sutlers is well understood. We have had so much picket duty to do and our food has been so bad that I had to buy chocolate and the common necessities that a person in our situation must have on such a short notice. But drop all that, I shall send every cent of wages hereafter to you to help you along and fo without these little things and try for once if I cannot subdue this habit of spending money.
Tell Al I will send the pipe Thursday or Friday by Adams Express and will pay for it. Father wrote me the same day you did and says he sends me with the regimental blankets two English blankets which I am very thankful for. I received also a letter from Lewis Coffin the same date and was very glad to hear from him and will answer it today. Give my respects to all my friends and Mr. Souder. Father has sent a good many blankets to the regiment and has done well.
Thursday is Thanksgiving. I don’t know ho it will pass here but I hope you will enjoy it and have a good dinner. I congratulate Al on his 22nd birthday and hope he will accept the pipe as my present to him as it is all I can send him but I hope it will no be long before I will be able to give him something better.
Give my love to the girls and tell them to write. Hoping this will find you all well, I remain your affectionate son, — Henry
A happy Thanksgiving to you all. — Henry

