William Henry Folker became a medical student and admitted as a member of the Royal College of Surgeons in 1851. He was apprenticed at Charing Cross Hospital in London to the surgeon James Fernandez Clarke, who was then sub-editor of The Lancet medical journal. In the census that year he was listed as a medical student, together with another student, Thomas Lea, at the home of James Fernandez Clarke at 23 Gerrard Place in Westminster. Whilst at Charing Cross, William won several prizes, including the final silver medal for clinical work.

In 1852, William became a Licentiate of Midwifery and also a Licentiate of the Society of Apothocaries of London.

In 1953 he was elected House Surgeon to the North Stafford Infirmary and took up residence in Stoke-upon-Trent. It is recorded that whilst in this post, he performed an amputation at the shoulder joint with only the porter and a night nurse to assist in the absence of any medical staff. The patient is understood to have made a good recovery. He held the positions of House Surgeon and Apothecary until 1856. In 1856 he commenced practice in Hanley at Bedford House in Havelock Place. He was married the following year to Ellen Jane Fourdrinier.

William took up a number of positions during 1859 and his name was entered onto The Medical Register on 1 January that year. He was elected Honorary Surgeon to the North Staffordshire Infirmary in which capacity he performed the first operation to excise a hard cataract. He held this appointment until 1890 when he took the position of Opthalmic Surgeon, relinquishing that in 1908.

That year, he also performed the first ovariotomy in the country. Furthermore, he joined the Volunteer Service and, in 1860 was appointed Battalion Surgeon Major to the 1st Battalion Volunteer Rifles who had their headquarters in Market Place in Stoke-upon-Trent. He was assisted by two other surgeons, Samuel F Gosling and William Dawes per the 1880 edition of Kelly's Directory of Staffordshire. He held that position until 1886 when he was decorated for long service.

He culminated as a Fellow of the Royal College of Surgeons of England, having passed his examination in 1864, the year that his son Herbert Henry was born and who was to follow in his footsteps as a surgeon. By 1871 he was the police surgeon.

William was a member of the time the North Staffordshire Medical Society when became the Staffordshire branch of the British Medical Society. He later became president (prior to 1871), at which occasion he read an address on the surgery of the extremities at which he compared surgery of the 1850's with that of more modern times.

Amongst the medical matters upon which William wrote, A Pharmacopoeia of the North Staffordshire Infirmary was published in 1870. According to The Provincial Medical Directory of 1871, he also contributed three articles to The Lancet Medical Journal, being Case of tumour of the tongue successfully operated on, Successful ligature of the external iliac and Successful ligature of the subelavian

By 1871 William had become Certifying Factory Surgeon for Hanley, Shelton,Etruria and Cobridge, a position legally required by the Factory Act. He served in that position about 1884 to 1904 and the 1892 edition of Kelly's Directory of Staffordshire shows him in this capacity in listed under Public Officers at Stoke-upon-Trent. His son Herbert Henry later also served in this post. Also in 1892, he took on the post of Consulting Surgeon.

In 1890, he was appointed Honorary Opthalmic Surgeon and was Senior Consulting Surgeon by 1899. Outside his hospital work, He was Vice President of the Infirmary from 1904 to 1905, and President in 1906.

William was interested in the welfare of the staff and was the instigator in 1899 to provide a home for the nurses. On 5 January that year, and as senior Consulting Surgeon, William presented a letter to the monthly meeting of the General Committee offering to start a fund with a donation of £100.

The amount required was £10,000 and donations quickly reached £7,800, including 105 guineas from King Edward VII. The Nurses Home was named after the King and the foundation stome was laid on 24 October 1902. William's name appears on the foundation stone.