The line is named after Nagahori-dori, a major avenue which it follows through central Osaka, and the Tsurumi-ryokuchi, a park in northeastern Osaka which hosted the
International Flower and Greenery Exposition in 1990. The line was built not only to provide access to the park during the exhibition, but also to relieve congestion from the Chūō Line. Its first segment opened on 31 March 1990 between
Kyōbashi and
Tsurumi-ryokuchi, at which time it was called the . Under its original plan, the line would have provided access to the
Osaka prefectural government offices near
Osaka Castle. However, the presence of underground artifacts around the castle area made this plan impractical, and the line was thus shifted farther south, which also provided a better connection with the Chūō Line. On 11 December 1996, the line was opened as far as
Shinsaibashi in downtown Osaka, and renamed the Nagahori Tsurumi-ryokuchi Line. On 29 August 1997, the line was further extended westward to
Taishō and eastward to
Kadoma-minami. Over the course of fiscal 2010, the 16 stations within Osaka City were outfitted with
automatic platform gates, similar to those already in use on the Imazatosuji Line. At Taishō, the first station to be so equipped, the gates started operation on 7 July 2010. The final station, Kadoma-minami, had them installed over the course of October 2011, with operation starting on 31 October of that year. File:Osaka Municipal Subway 70 series.jpg|Platform screen doors at Osaka Business Park Station == Line data ==