DENVER (AP) — Janus Henderson Investors says that "Bond King" William H. Gross is retiring to concentrate on his personal assets and private charitable foundation. The 74-year-old Gross will retire on March 1. Gross founded the investment firm Pimco in 1971 and helped build it into one of the world's biggest asset managers before leaving for Janus in 2014. When Gross left Pimco his fund was the biggest bond fund in the world, valued at $222 billion. Gross has attracted hundreds of millions of dollars to the funds he's run during his career.