On Thursday, the state of Illinois found the perfect way to celebrate Valentine’s Day — passing a bill to legalize same-sex marriage. For the first time in American history, same-sex couples in 10 states will now be able to marry those they love.

A recent book by Rodger Streitmatterdetails the stories of 15 powerful same-sex couples. The following is excerpted from this book, which you can purchase here.

Walt Whitman & Peter Doyle, 1865-1892: Revolutionizing American Poetry

Communicating Their Love In Letters

Whitman and Doyle began writing to each other in 1868, the first time they were apart after beginning their outlaw marriage. The men were separated because Whitman visited his family in New York, while “Pete the Great” had to stay in Washington to work. Their correspondence continued, off and on, whenever they were apart, for almost two decades.

In the first surviving letter, Doyle exclaimed, “I could not resist the inclination to write to you this morning it seems more than a week since I saw you.” Whitman then responded, “I think of you very often, dearest comrade—I find it first rate to think of you, Pete, & to know that you are there, all right, & that I shall return, & we will be together again.”

In the six weeks that the men were apart that first time, Doyle wrote at least seven letters and Whitman wrote at least 11.

During that period as well as during later ones, Whitman routinely began his letters with the words “My darling” and ended them with phrases such as “Love to you, my dearest boy” or “So long, dear Pete–& my love to you as always.” Doyle ended his letters by writing “Pete the Great” or “Pete X X,” using the X’s to represent the kisses he sent his partner.

Outlaw Marriages by Rodger Streitmatter, © 2012 by Rodger Streitmatter. Reprinted by permission of Beacon Press, Boston.