Port Union is on Princeton-Glendale Road (Ohio 747) around the intersection with Port Union Road. The West Chester Twp. village was so named because it was a port on the Miami-Erie Canal. It was laid out by William Elliott and first named McMaken's Bridge in honor of an early settler who built the first house in 1827. There was a post office there from May 11, 1850, until Jan. 31, 1903. Port Union also was on the Cincinnati & Richmond Road (now Norfolk Southern).
The Hamilton Daily News, Thursday, Nov. 22, 1888, under the headline "Port Union vs. Rialto," carried the following item: "The post office muddle between Port Union and Rialto is assuming serious proportions, to the great discomfiture of the residents of the former place. It seems that a petition was gotten up which was numerously signed by residents of Port Union without much attention being paid to the substance matter state therein, and when looked over the postmaster at Port Union he discovered it state that more mail matter came to Rialto then to Port Union. This caused the postmaster of the latter place to keep an account of the number of pieces received; for six successive days, and for each day he found there was a great deal more came to Port Union than to Rialto; in this connection it might be stated that the proprietors of the mills at Rialto do not receive their mail matter there, but at Lockland, Hamilton County. The postmaster at Port Union after his observation of the mail received at the two places, sent his report to the department at Washington. The outcome of the post office war will be watched with much interest by people in the localities named."