Garrison Block

The Garrison name first enters the scene in 1862 when Abner Garrison (1800-1876) purchased the lot. At this time, one of Abner’s sons, Levitt D. Garrison (1837-1916) was engaged in a grocery and crockery business with Charles W. Collins for a couple of years until they split in 1865. Collins continued his establishment in the Garrison block location into the 1870s, perhaps right up until a new structure was erected in 1877. The ownership of the block had by that time been transferred from Abner Garrison to another son, Charles H. Garrison (1823-1900), who was president of the Cortland and Homer Horse Railroad (think horse-drawn trolley!). 

Charles’ brother, Levitt, moved his grocery business into the new block, but I had some trouble getting the exact location straight since I saw an article stating that he had decided in 1878 to move into the north store (what is number 17 today) and yet everything else referenced placed him in the south store!
Fortunately, there's this fun correction in the Cortland Standard:
“L. D. Garrison is having a hard time of it at the hands of the newspapers. The Democrat a few weeks since assigned him to the store lately occupied by H. H. Pudney, and last week The Standard, through somebody's blundering, gave him the north store in the new Garrison block, and put Tanner Bros, in the south one. By transposing the words north and south the truth will be arrived at, and Garrison will have peace.” 

Thus, in 1878 we can place L.D. Garrison in no.21, and Tanner Bros. dry goods in no.17. In 1884, a fire started in a covered entrance in the rear of the neighboring Wickwire block and destroyed that building together with the Garrison block. When Garrison’s was rebuilt, it very nearly matched its predecessor except for some small differences: the arches above the windows today feature light-colored stone with dark keystones, but the original block had arches and keystones in a matching color. Additionally, the previous structure had belt courses separating the floors that were made of cut stone from the Split-Rock quarry near Syracuse, while the rebuilt block did not replicate this feature. 

"History of Cortland County" by H.P.Smith (1885)
Cortland Standard newspapers
"Past and Present: A Historical and Descriptive Sketch of Cortland, N.Y." by D. Morris Kurtz (1883)