Rabbi Moshe Feinstein was recognized during his lifetime as the posek hador, the final decisor in halakhic queries, by much of the world's Orthodox Jewish community, due to his reputation as a talmid chacham with profound knowledge in all areas of Torah. The most difficult questions were often mailed to him. In 1959, a compilation of these questions related to the laws of Orach Chaim were printed in the first volume of Igros Moshe. Later volumes were printed over the next twenty five years, with the publishing of the sixth volume in c. 1985. The remaining two volumes were published posthumously, largely based on manuscripts, with the final printing in 2011. Altogether, the series includes thousands of responsa. In addition, an index titled Yad Moshe was published, listing different ideas and where one can find relating halakhos in the Igros Moshe. His son-in-law, Rabbi David Tendler, translated some of Igros Moshe in a work titled Responsa of Rav Moshe Feinstein: translation and commentary.
