What year did the 10 cent Robert Frost stamp come out?

The 'Robert Frost', 10 cent stamp, Scott Catalog #1526, came out March 26, 1974.

(Scott Specialized Catalog of US Stamp 2011, page 138), with over 145 million stamps issued (page 530).

It was first issued at Derry, N.H. for a total of 500,425 "First Day Covers" (page 397).