One of the oldest commercial buildings remaining downtown, and certainly inside the Downtown Loop...The building was completed in 1874, originally as home to the Brackett Brothers Drugstore. Seiden’s Furs opened in 1921 and became one of the Central Business District’s oldest businesses before it shut its doors in 2007. ...
https://www.bizjournals.com/kansascity/ ... sally.html
310 Delaware retail building (1866-67) aka Coates Theater
Pacific House Hotel (1868)
Major William Warner mansion, 1021 Pennsylvania (1868)
Tootle, Hanna & Leach Dry Goods Building, 412 Delaware (1869)
H.H. Morgan & Co. Building, 308 Delaware (1869-73)
Cromwell Lofts, 528 Walnut (1871)
1070 Washington house (1870s)
St. Patrick's Church, 8th & Cherry (1874-75)
Brackett Brothers Drugstore/Seiden Fur Building (1874)
First Board of Trade Building, 500 Delaware (1877)
Fifth Street (Delmonico) Hotel at 5th and Broadway (1879)
Deere, Mansur & Company, 1104‐1106 Santa Fe Street (1879)
It appears to be the oldest commercial building inside the Downtown Loop though.