When Sister Elaine Lachance devoted herself to a religious life straight out of high school in 1959, her religious order had more than a dozen convents in the U.S. with nearly 260 sisters.

Today, the Good Shepherd Sisters of Quebec, based in Canada, has just five convents in Maine and Massachusetts with 56 sisters. The youngest is 64 years old, and it’s been more than 20 years since a new member joined.

Rather than leave the future of the convents to prayer and chance, Lachance has turned to the Internet. She’s using social media and blogging to attract women who feel the calling to serve God and their community.

She says she had her awkward moments when she began using Facebook and writing blog posts.

“But I knew I had to go there, that I had to do it,’’ said Lachance, who turned 70 on Sunday. “You have to go where the young people are. And that’s where they are.’’

The number of nuns and sisters has plunged through the decades as more career opportunities for women opened, parochial schools closed and sisterhood became less visible. Generally, a nun lives a cloistered, contemplative life in a monastery, while sisters live and work within their communities.

In the U.S., the count has fallen from about 180,000 in 1965 to 55,000 last year, a drop of nearly 70 percent, according to the Center for Applied Research in the Apostolate. In 2009, their median age was 73, with 91 percent of them 60 and older.

At one time, women would join the sisterhood through word of mouth or their personal interactions with sisters, said Lachance, vocation director for the Good Shepherd Sisters. But now, many younger women aren’t even aware it’s a choice.