The locomotives were produced by H. K. Porter, Inc, of Pittsburgh, Pennsylvania. Two were purchased in 1880 (Nos. 368, 369), two more in 1882 (Nos. 487, 488), one in 1884 (No. 643), one in 1885 (No. 672), and two more in 1889 (Nos. 1009, 1010), for a total of eight. Six of the locomotives were named after major historical or literary figures in 1889, at the suggestion of the Japanese Consul of New York City, Takagi Saburō, who found appeal in the similar practice seen in the United States at the time. Thus, the six engines were named "Yoshitsune", "Benkei", "Hirafu", "Mitsukuni", "Nobuhiro", and "Shizuka", respectively. The final two engines did not receive names.