Last Sunday, Lynn Feng ’06 and 11 Yale friends awoke one-by-one to a lower West Side apartment of empty wine bottles and scattered brains. “What happened last night?” they asked each other.

A simple answer said it all: open bar and another 21st birthday.

“Where’s my shirt?” asked Feng, rummaging through a pile of the previous night’s party favors: white cotton T-shirts with the image of an orange lily and a faded “21,” the same logo that appeared on the professionally-designed online invitation for classmate Lily Oliver’s ’06 21st birthday.

Twenty-one is the birthday that garners more celebration among Americans than any other and contributes significantly to the junior year social scene at Yale. Popular local restaurants have more than one 21st birthday party scheduled each weekend for the remainder of the school year. While some students opt for smaller parties in restaurants or suites, many go all-out for their 21st, with open bars, long guest lists and plenty of food to balance the alcohol. The birthday has even received attention from legislators in several cities and states increasingly concerned by a tradition among college students of taking 21 shots on their special day.

“I do know a couple people who did the 21 drinks thing,” said Oliver, who estimates she generally has at least one 21st birthday party to attend every weekend. Oliver bused many of her friends down to the New York restaurant Butter for a night of dancing, drinking and hors d’oeuvres on a private floor. “I don’t know how many drinks I had [at my party], but I’m sure it was no more than 10.”

A few of Oliver’s 130 some-odd guests — which included this reporter — lost track of the night sometime after arriving via chartered bus to the trendy New York restaurant known for its de riguer fusion cuisine and the frequent visits of starlet Ashley Olsen. But if guests cannot remember everything that occurred on that glossy wood dance floor, they might be in luck, because Oliver said she plans to upload the party’s Web site, www.lilyoliver.com, with pictures from the night that were taken by a professional photographer.

It might seem extravagant to have a photographer, florist, T-shirts, Web site, chartered bus, endless drinks and avocado and shrimp bite-size tacos galore. After all, the price tag to rent a space at Butter with open bar and appetizers can be anywhere from $12,000 to $15,000, not including DJ, party favors and other amenities. And though most students stay in New Haven to celebrate their big day, it still costs upwards of $3,000 to have an open bar and appetizers for 100 guests at the most common 21st birthday sites, including Adulis, Anna Liffey’s and Backroom at Bottega.

For Alex Schwed ’06, his party at Adulis in October was his parents’ 21st birthday present to him.

“I wanted to do something fun because I hadn’t really done much in terms of birthday parties the last few years,” Schwed said.

Although he said he did not drink very much because he was too busy mingling with some of the 200 guests on the invite list, Schwed said he did know one Yale friend, who he declined to name, who wound up in the hospital on her 21st birthday after trying to make it to 21 drinks.

Although the prevalence of underage drinking would seem to minimize the importance of the 21 mark, students still see the birthday as an important milestone worthy of sometimes excessive celebration. Turning 21 at Yale means coming one step closer to graduation and is the last legal benchmark to becoming a full-fledged adult. But instead of dreading the symbolic transition to the burdens of adulthood, students use a big party to celebrate their change in status.

For example, Julie Baine ’06 said she chose to have her party at Anna Liffey’s so that her parents could come to meet all her friends and celebrate her rite of passage with her.

“I wouldn’t have had a big party at all if my family couldn’t have made it,” said Baine, who said she felt no pressure to throw a big party, but simply wanted to bring the important people in her life together.

Both Oliver and Schwed agreed with this sentiment.

“It’s such a once in a lifetime thing,” Schwed said. “It’s nice because it makes the junior year party landscape really interesting. And, I mean, if you didn’t have a bat mitzvah, why not?”