Blame it on my niece.  She posted a photo she snapped, on Main Street in Princeton, Missouri, of a building with the word TELEGRAPH near the top,  spelled out with bricks.  She learned from the owner that in the 1890s, the building was built to house the newly contracted telegraph service for the town.  (The above image is from Google Street View.)

Just curious to know more, I googled words like telegraph and Princeton,  without the intended result.   BUT, what did result led to the fascinating 1845 book, The American Electro Magnetic Telegraph,  by Samuel Morse's associate, Alfred Vail, 

Many hams, perhaps most, know Alfred Vail as the unsung hero of the Morse Code.  He deserves credit for the code sending hand key used, beginning with the 1844 Washington-to-Baltimore demonstration paid for by the US Congress.  Many consider him to be the originator of the dot-dash alphabetic code, instead of Morse.  Vail would have us give the credit to Morse.  He did, however, take pains to make sure posterity knew the "Register" used to record the received dots and dashes was his own design.

For a wonderful read about Vail's Register, and how it came to be owned by Cornell University, see the article by John Casale, W2NI.  It was published in the May 2001 issue of the quarterly journal of The Antique Wireless Association.  The online version is available at telegraph-history.org here .

Vail's book is the official Report to Congress documenting a host of interesting history related to the development of the telegraph.  

One section that caught my attention was entitled Mode of Secret Correspondence.  From the outset, there was a recognized need for communication to be kept private.  Vail gives us an  interesting look at some methods used in the decade before the American War Between the States.

These slides, including 3 ciphers, are snips from the Alfred Vail report to Congress: