Sister cities of Nagaoka, Niigata

Nagaoka (長岡市, Nagaoka-shi) is a city located in the central part of Niigata Prefecture, Japan. It is the second largest city in the prefecture, after the capital city of Niigata. Nagaoka is located at longitude 138°E and latitude 37°N.

The size of Nagaoka increased on April 1, 2005, when the town of Oguni (from Kariwa District), the village of Yamakoshi (from Koshi District), the town of Nakanoshima (from Minamikanbara District), and the towns of Koshiji and Mishima (both from Santō District), were absorbed into Nagaoka. As of June 1, 2005, the city had an estimated population of 237,115 and a population density of 450.88 persons per km². The total area was 525.89 km².

It once again increased on January 1, 2006, when the city of Tochio, the towns of Teradomari and Yoita, and the village of Washima (all from Santō District) were absorbed into Nagaoka.

And finally, one March 31, 2010, the town of Kawaguchi (from Kitauonuma District) was absorbed into Nagaoka. As of November 1, 2010, the city has an estimated population of 283,343 and a population density of 318.83 persons per km². The total area is 890.91 km².