Robert Indiana, the Pop artist whose bold rendering of the word “love” became one of the most recognizable artworks of the 20th century, gracing hundreds of prints, paintings and sculptures, some 330 million postage stamps that he authorized and countless tchotchkes that he did not, died on Saturday at his home in Vinalhaven, Me. He was 89.

His lawyer, James W. Brannan, said the cause was respiratory failure.

Mr. Indiana’s famous image features the word L-O-V-E rendered in colorful capital letters, with the first two letters stacked on top of the other two, and the letter “O” tilted as if it were being swept off its feet. Since he designed the earliest versions, in the 1960s, the logo has acquired a life of its own, appearing on everything from posters and album covers to T-shirts and jewelry.

Mr. Indiana called it the 20th century’s “most plagiarized work of art,” and he kept a collection of knockoffs in his home, a historic Victorian building, to prove it.

[Read about the lawsuit that accused two men of tainting the artist’s legacy.]

To be sure, he had a hand in spreading the word, creating many artworks in different mediums based on the motif. And he designed the red, blue and green version that was originally issued as an eight-cent stamp by the United States Postal Service for Valentine’s Day 1973. It has since become one of the most popular holiday stamps in the United States.