Paul Allen, longtime owner of the Portland Trail Blazers and one of the world's richest men, died Monday in Seattle from complications from non-Hodgkin's lymphoma. He was 65.

Allen, born in Seattle in 1953, was a fixture in the Northwest for most of his life. He co-founded Microsoft with childhood friend Bill Gates and built the startup computer company into one of the world's most successful corporations, turning Allen into a billionaire.

Forbes values his fortune at $20.3 billion, making him the world's 21st richest person. The magazine tallies his total philanthropic contributions at $2 billion.

Allen used his considerable wealth in a variety of ways over the years, investing in a host of companies, donating to countless charities and accumulating pricey toys, and the last three decades of life were defined by his passions: sports, the arts and science. After a life-threatening bout with Hodgkin's disease, Allen resigned from Microsoft in 1983. And although he retained a significant chunk of the company's stock, Allen shifted his priorities to his passions.

He purchased the Trail Blazers five years after resigning from Microsoft and went on to buy the Seattle Seahawks of the National Football League and become a part owner of the Seattle Sounders of Major League Soccer. It's unclear what will happen to the ownership of these teams with his passing, but Allen's legacy will live on regardless through his charitable endeavors.

Those include the Allen Institute for Brain Science, the Experience Music Project in Seattle (now known as the Museum of Pop Culture) and the Oregon Shakespeare Festival in Ashland. In July 2010, Allen pledged to give the majority of his fortune to philanthropy after his death.

Microsoft was by far Allen's biggest success, and after he amassed his initial fortune, his business ventures, orchestrated through Vulcan Inc., were erratic. For every hit (he was an investor in DreamWorks Animation) there seemed to be a miss (Charter Cable). His multibillion-dollar investment portfolio included large stakes in Plains All American, real estate holdings and more than 40 technology, media and content companies.

But for the majority of Oregonians, Allen will be most remembered for his long tenure as owner of the Blazers, Oregon's most beloved sports franchise and one of his greatest passions. Allen purchased the Blazers in 1988 and was intimately involved in the team's operations until his death.

A self-confessed basketball fanatic, Allen regularly evaluated college prospects in the walk up to the yearly NBA draft and relished being in the Blazers' war room on draft day. If Allen developed a love for a certain player, odds are that player would be retained regardless of what the Blazers' basketball talent evaluators thought.

Allen so loved the team, he once paid for a private television production crew to travel to Redmond to film and broadcast live a preseason game against the Denver Nuggets to his yacht outside Africa.

Allen's tenure as Blazers owner was rife with controversy but mostly successful. Under his ownership, the Blazers qualified for the playoffs 23 times and made five trips to the Western Conference Finals. Twice the Blazers played in the NBA Finals -- in Allen's second season as owner in 1990 and in his fourth season in 1992.

And Allen was vital to the success. His immense wealth and willingness to spend allowed team general managers to stockpile resources and talent, which helped level the playing field for the small-market Blazers. But his desire to win regardless of the costs did not come without contention.

Under general manager Bob Whitsitt, the Blazers made as many headlines for their off-the-court troubles as they did for their on-the-court success. Whitsitt spent large sums of Allen's money -- as much or more than any team in the NBA at the time -- to build a roster loaded with talented players. But Whitsitt often ignored a player's character and past transgressions.

The Blazers reached the Western Conference Finals in 1999 and 2000, but were ridiculed nationally as the Jail Blazers because so many players had been arrested, fined and/or suspended. Ultimately, Whitsitt's approach backfired. He resigned in 2003 and Allen said the franchise would shift its focus and place a greater emphasis on a player's character.

"We are changing our approach," Allen told The Oregonian. "It's not business as usual at the Trail Blazers."

The rebuilding effort was painful. The Blazers endured three losing seasons --they finished with the worst record (21-61) in the NBA in 2006 -- and missed the playoffs six consecutive seasons. Attendance and fan interest sharply declined. In 2006, after years of financial losses, Allen said the Blazers had a broken economic model and he put the team up for sale.

But less than a year later, Allen had a change of heart and the franchise went on to dig itself out of the rut. With shrewd draft-day trading and luck, the roster was overhauled under general manager Kevin Pritchard and the Blazers returned to the playoffs in 2009 with a talented -- and high-character -- roster.

But injuries derailed that momentum and went on to define the franchise for years as stars such as Brandon Roy, Greg Oden -- the No. 1 overall pick of the 2007 NBA draft -- and countless other players suffered season-and career-threatening injuries. The Jail Blazers had evolved into the Frail Blazers.

Allen unexpectedly fired Pritchard about an hour before the 2010 NBA draft in perhaps the oddest move in franchise history, and that era was over.

But not Allen's passion for the Blazers. Allen hired Rich Cho as general manager after Pritchard, but that marriage lasted just 10 months. Neil Olshey replaced Cho in 2012, he hired Terry Stotts as coach and drafted Damian Lillard with the No. 6 overall pick of the 2012 NBA Draft, and the trio are still entrenched as the cornerstones of the franchise to this day.

Allen was first diagnosed with non-Hodgkin's lymphoma in 2009 and underwent intensive chemotherapy, but he continued to regularly attend Blazers games -- though he was noticeably thinner and had less hair.

By summer 2010, Vulcan announced that Allen was no longer dealing with medical issues and he was a regular at games, the occasional practice and, of course, the Blazers' draft room. But it's common for lymphoma to return to patients within two years of finishing chemotherapy and treatment is much more complicated the second time around. He revealed a second occurrence of the disease Oct. 1 -- two weeks before his death.

"Paul Allen was the ultimate trail blazer -- in business, philanthropy and in sports," NBA Commissioner Adam Silver said Monday in a news release. "As one of the longest-tenured owners in the NBA, Paul brought a sense of discovery and vision to every league matter large and small. He was generous with his time on committee work, and his expertise helped lay the foundation for the league's growth internationally and our embrace of new technologies. He was a valued voice who challenged assumptions and conventional wisdom and one we will deeply miss as we start a new season without him. Our condolences go to his family, friends and the entire Trail Blazers organization."

Joe Freeman | jfreeman@oregonian.com | 503-294-5183 | @BlazerFreeman