LP graduated from Walt Whitman High School in 1996. Afterwards, she moved to New York City from Huntington, Long Island and adopted the name "LP" during that time. David Lowery of the band Cracker saw her performing and featured her on "Cinderella", a hidden track on the band's 1998 album, Gentleman's Blues. Lowery followed up by producing her debut album, Heart-Shaped Scar, released in 2001 through Koch Records.
LP's sophomore album, Suburban Sprawl & Alcohol, was released in June 2004 through Lightswitch Records. On the record, she collaborated with songwriter and music producer Linda Perry. However, in spite of extensive touring to promote the release and positive reviews from music critics, the album failed to gain widespread recognition.
In 2006, LP appeared at the music conference, South by Southwest, and reportedly sparked a bidding war amongst major music labels, eventually being signed by L.A. Reid to his Island Def Jam Music Group record label, part of the Universal Music Group. However, due to artistic differences she left the contract. She signed with SoBe Entertainment in 2007, an independent record label, with the album tracks she had written at the major label. "Love Will Keep You Up All Night", one of the tracks she had written at Island Def Jam Music Group with Billy Mann, was released in late 2007 on the Backstreet Boys album, Unbreakable. LP wrote and performed "Wasted", from her album Suburban Sprawl & Alcohol, which was the theme song for a television show "South of Nowhere" on The N, currently known as TeenNick. MTV's The Hills also featured LP's song "Damage Is Done" in mid-2010, and it was released on iTunes. During 2009, LP started writing songs for other artists, working extensively on the Heidi Montag album, Superficial (Warner Music). She co-wrote the single, "More Is More", as well as the album tracks, "Twisted", "Hey Boy", and "Love It or Leave It". She also co-wrote other tracks for and with Montag, such as the Cathy Dennis co-write, "Look How I'm Doin'", "I Do This", and "Who's That Girl". A song she wrote with Alexander Kronlund,"Standing Where You Left Me", was released on Erik Hassle's debut UK album, Pieces (Roxy/EMI/Universal).
In August 2010, it was announced that LP had signed with RedOne's record label, 2101 Records.
She landed her first major breakthrough as a songwriter, co-writing Rihanna's song, "Cheers (Drink to That)", featured on Rihanna's fifth studio album Loud, released on November 12, 2010 on Def Jam Recordings. "Cheers" features a vocal hook performed by LP (taken from Avril Lavigne's "I'm with You"). In a 2010 interview with MTV News, Rihanna said: "I love that song ['Cheers']. That is one of my favorite songs on the album. It makes you feel like celebrating. It gives you a great feeling inside like you want to go out and have a drink. ... People can't wait for the weekend."
LP's major label songwriting breakthroughs continued, as she co-wrote "Beautiful People", performed by Christina Aguilera. The song is featured on the Burlesque: Original Motion Picture Soundtrack album, which was released on November 22, 2010 through RCA Records.
In June 2011, LP co-wrote "Afraid to Sleep" which was performed by NBC's The Voice finalist Vicci Martinez and reached #10 on iTunes Top Singles Chart. In September 2011, she signed a deal with Warner Bros. Records. Shortly after, "Into the Wild", written and performed by LP, was prominently used in a Citibank national television advertisement campaign. In April 2012, she released her first major label album Into the Wild: Live at EastWest Studios, a five-song live extended play, and started touring extensively including festivals such as SXSW, Bonnaroo, Lollapalooza, Bumbershoot, Tropfest as well as Tokyo's Sonic Boom and London's Hyde Park. In 2012, she became the first female Martin Guitar Ambassador.
In May 2012 she featured as Artist of the Week in Vogue magazine. Over the following two years, she completed the recording of her third album that included collaborations with Billy Steinberg, Isabella "Machine" Summers (from Florence and the Machine), Josh Alexander, Claude Kelly, Justyn Pilbrow, Carl Ryden and Rob Kleiner. The album was produced by Rob Cavallo, Warner Bros. Records' chairman and producer. On April 1, 2014, it was announced that LP's third full-length studio album would be titled Forever for Now, and was scheduled to be released on June 3, 2014. The album was promoted by the lead single "Night Like This". Following the album, a second single "Someday" was released in June 2014 in Canada. On September 16, 2014, a music video for "Tokyo Sunrise" officially premiered on Time magazine's website.
In September 2015, the song "Muddy Waters", the first single from LP's upcoming fourth studio album, was released.In June 2016, this song featured in the violent and emotionally charged closing scene of the season four finale of Netflix's original series Orange Is The New Black. In November, the second single, titled "Lost on You", was also released, while she held a residency at the No Vacancy club. Both songs originate from a collaboration with Mike Del Rio. An EP is due to be released in early 2016.