William Christopher O'Hare was born in Washington, DC, to Albert O'Hare and Mary Eva Brown just two years after the end of the Civil War. He had several siblings who followed him, including George Langdon (12/1871), Joseph Vincent (10/30/1872), Mary Ellen (6/1874), Mary Eva (7/11/1876), Anna Elizabeth (11/1877), Ellen Teresa (10/1879), and Henrietta Josephine (1/1883). The 1870 and 1880 censuses taken in Washington showed Albert to be a grocer, likely with his own store given that he also had live-in domestics. This modicum of wealth also likely assisted the O'Hares in obtaining music lessons for their oldest child. It was difficult to locate specifics, but he obviously had training in harmony and theory as well as piano, organ, and possibly other instruments. This is also evident as a foundation for his later career. In spite of his talents, O'Hare (or his parents) had a plan B in mind, as he was graduated from a business college. Still, there is evidence that he briefly led a concert band in Washington in the mid-1880s before he moved down to the Deep South.

In 1888, Will got a job as the director of the Grand Opera House in Shreveport, Louisiana. A historical look at the type of shows that played at this venue suggest that it was not much beyond a fancy vaudeville palace, but one that was highly regarded nonetheless. Shreveport was right at the Louisiana/Texas border, near Marshall, Texas. It was there that Will married his Tennessee-born bride, Maria Carlotta "Lottie" Slater on July 23, 1890. (Many sources show her middle name as Charlotte, but her death certificate shows Carlotta.) Lottie and William had two boys, William Crockett (5/15/1891) and Vincent Slater (9/6/1894), both born in Shreveport. During his nearly 13-year tenure running the musical programs at the Opera House, O'Hare took up other duties and musical avocations as well, executing them well enough that they would effectively advance his later career. He warranted a mention in The Genealogy and History of the Shreve Family from 1641, printed in 1901:

Among O'Hare's earliest works was The C.S.A Grand Medley, actually a fine arrangement of familiar Southern or "Confederate" tunes with some American Civil War ties. He also arranged liturgical works, including a Te Deum, premiered at St. Mark's church, and Jewish high holy days favorite We Bend, first performed next door to St. Mark's at the B'nai Zion Temple. The Southern city of Shreveport had an active music scene in the black community, part of which was either close to or actually where the O'Hares resided. Between the locals and the traveling troupes, Will had a lot of exposure to music trends among African-Americans, and would soon embrace them as an extension of his performing and arranging work. One of his first published piano works, presumably also orchestrated for dance, was Cotton Pickers, published in 1894. It was cast more or less in the up and coming cakewalk style, with some mild syncopation. (A couple of pieces with the same title appeared in 1899 with more syncopation, but by different composers, including William Braun, made popular by John Philip Sousa, and sometimes confused with O'Hare's work.) Cotton Pickers would take a while to catch on, gaining popularity along with a couple of his later syncopations. By 1897 he was a professor of music [whether he was degreed or not was often immaterial at that time] at the highly regarded Kate Page Nelson's Seminary.

Most information about O'Hare through early 1898 has more to do with his arranging and conducting activities in Louisiana than anything to do with composition or New York. However, in 1898 he managed to get one of his most important pieces published by the New York firm of M. Witmark, namely Levee Revels. This may have been more of an ancillary exercise for Will, as also making an appearance that year were much less mainstream works, including the concert waltz The Awakening of Venus, and the unusual "Mystery Dance," Heliobas. Just the same, Levee Revels soon became a conduit for O'Hare, eventually being picked up by Sousa's band (under the baton of Arthur Pryor among other organizations, and part of the early cache of recorded ragtime pieces. The following year, 1899, his output was nearly as eclectic, covering liturgical and popular music, and the release of Plantation Pastimes, which while allegedly copyrighted in 1900, was listed in The Witmark Amateur Minstrel Guide and Burnt Cork Encyclopedia printed in 1899. A deep search of the 1900 census did not reveal a listing for O'Hare. However, he was reportedly residing at the City Hotel in Shreveport, also working for them as an entertainment director.

It is not entirely clear at what point the Witmark organization started tapping into Will as an arranger, but by 1900 he was traveling quite often between Shreveport and New York City, providing them services in that guise. It was clear by 1901 that he could make a lucrative living in New York as a Witmark employee, so he relocated there for good. Over the next three decades, O'Hare would arrange both religious and popular works for everything from piano to orchestra, and some very effective vocal settings as well. Witmark would continue to publish his own pieces, including the popular Cottonfield Capers. He would compose a couple more syncopated works through 1907, but Will's ragtime-based output was minimal at best, and his work as an arranger soon took precedence.

Lottie was less than enthusiastic about moving her young sons to the big city, and remained behind in Shreveport for a while in the early 1900s. Once she finally moved to New York, internal strains in either the environment or their relationship took their toll, and the O'Hares would separate, although it is not clear exactly when. To exacerbate this dearth of information, the 1905 New York State census yielded no results, nor did the 1910 Federal census, which may be a coincidence, but may also be intentional on the part of Will. Listings in Manhattan phone directories and the 1920 census show variations on his name, including William C. O'Hara, and William C. Christopher, a variant found frequently from the mid-1910s into the late 1920s. Those listings showed him always to be a musician or music writer. Infrequent mentions in the Music Trade Review and the New York Dramatic Mirror confirm the same. However, a number of his original compositions and arrangements during this period were published by houses other than Witmark.

O'Hare continued his career as an organist, aligning himself with the Ascension Memorial Church, an Episcopal church in Ipswich. He also gave organ recitals at various venues in New York, New Jersey and Connecticut throughout the 1910s. There was even a series of multi-tune medleys and single piano rolls that were comprised of custom O'Hare arrangements. While none of his compositions really made a splash following his ragtime hits, his continuing work for Witmark was solid in presenting the works of other composers. Among those he had known during his days in Shreveport was stage composer Victor Herbert, with whom he collaborated with a few works, including the operetta Naughty Marietta. Will also spent many years as a choir director in conjunction with his organist activities, and taught music as well, all of these activities continuing until nearly his death. Remembering his secondary roots in Louisiana, O'Hare advocated for a number of artists of any race in the fields of popular music and jazz, getting them published or into performance venues.

While he maintained a relationship with his sons, and later, his grandchildren, Will never reunited with his wife. Both of them being Catholic, there was no divorce. At some point in the 1920s she moved from New York down to the area of San Antonio, Texas, where she was found in 1930 census, listed as widowed above a crossed-out indicator for married. Her son William would move in with her in the early 1930s, and they were listed in Bexar County, Texas, in the 1940 census, this time with Lottie acknowledging she was still married. That same year, Will was still in New York, residing at St. Paul's Hotel in Manhattan, and listed as a writer of music, although his last compositions of note had been a number of film cues written for pre-sound pictures in the mid-1920s. Lottie died in San Antonio on May 24, 1944, at the state hospital, suffering from bronchial pneumonia and "senility." Although some sources claim that William O'Hare died in 1943, he actually survived three years more, passing on at Roosevelt Hospital in New York City on October 22, 1946. He was buried in the family plot in Washington, DC.

As for his legacy, O'Hare was not the first in published ragtime, but among the first, and not the most authentic, but able to incorporate and lot of ethnic and regional authenticity in his handful of works. Levee Revels and some of his other works are still performed more than a century after their introduction, and his role with Witmark, one of the more liberal publishers when it came to being color-blind in terms of talent, is possibly understated, some of it clearly unknown. His legacy may be more about what he did for others in the field of ragtime music and similar disciplines, but he should be recognized for his own merits as well.