When was the last star added to the U.S. flag was for the state of Hawaii?

4th July 1960

The current American flag was adopted on July 4, 1960. The American flag originated in the mid-18th century from flags used at the time of the American War of Independence with Britain. Congress officially set the design of the American flag in June 1777, stating that it should be 13 alternating red and white stripes, with 13 white stars on a blue field as there were 13 original member states in the newly formed Union. As new states joined the country a new star and stripe were added to the American flag. In 1818, the American flag's design was changed to the original one of 13 stripes. Any new states were now represented by a white star only and would be added to the American flag on July 4th of the year they joined. Up until 1818, there was no specific pattern for the stars to follow and this led to a few different designs until the president stated they should be placed in parallel rows. The last star, representing Hawaii was added in 1960, and it became the 27th version of the American flag.

worldflags101.com/u/usa-flag.aspx no longer exists

Executive Order of President Eisenhower dated August 21, 1959 - provided for the arrangement of the stars in nine rows of stars staggered horizon tally and eleven rows of stars staggered vertically. This is the current flag of the United States. Hawaii was admitted as the 50th state on August 21st, 1959. The 27th flag of the United States became the official flag on July 4th, 1960.

https://www.chamberofcommerce.org/usflag/the.50.star.flag.html

Hawaii became a state in 1959 here is the link https://en.wikipedia.org/wiki/Hawaii

This is a perfect example of why pertinent information needs to be taken from the link.

The question doesn't ask when Hawaii became a state, but knowing that happened in 1959 makes the star answer of 1960 appear incorrect, until you read that the stars are not officially added until July 4th. Hawaii was admitted in August of '59, hence its star was not added until the following 4th of July, 1960.