Construction sheet for the 1959 (49-star) <a href="https://en.wikipedia.org/wiki/Flag_of_the_United_States" class="extiw" title="w:Flag of the United States">Flag of the United States</a>.  This is the specification published in conjunction with <a href="https://en.wikisource.org/wiki/Executive_Order_10798" class="extiw" title="s:Executive Order 10798">s:Executive Order 10798</a>, which defined the flag.
U.S. Government
1959
Scanned from a microfilm printout of the January 6, 1959 Federal Register, page 80. This is printed there as the attachment to Executive Order 10798.