Before about 100 people at the hospital's main entrance, Johnson's outstretched hand helped flip the switch to light the tree outside, drawing "oohs" and "aahs" from the crowd.
"Joshua is why we are here," said Angela Crowder, occupational therapist and pediatric program leader at the hospital.
Before Johnson was referred to Washington County Hospital, he could not follow objects with his eyes and he could not pick up items, said his grandmother, Robin Grove of Hagerstown.
"He couldn't do anything," Grove said.
At Washington County Hospital, Johnson started undergoing physical and occupational therapy, which included exercises like holding items over his head, gradually leading him to hold his head up and focus his eyes, Grove said.
Johnson can now pick items out of a bowl and is sitting up with assistance, Grove said.
"This program has been awesome," Grove said.
Johnson's mother, Mandi Shoemaker, also was in attendance Sunday.
Money is raised for Tree of Lights through individual light donations that range from $10 to $500, said Jean Goodnight, chairwoman of the event.
Donations start in October and are collected until Dec. 31, Goodnight said.
Tree of Lights raised $17,200 for pediatric rehab care last year and organizers hope they can be that successful again.
Raising money is vital for the program because families of children in the program often run out of benefits before the children get all the help they need, Crowder said.
Despite the money that has been raised to help families, there is still more demand for the help, Crowder said.
Tree of Lights was celebrated in a ceremony starting at 5 p.m. Sunday. It included words from James P. Hamill, president and chief executive officer of Washington County Hospital, and holiday songs performed by The Saint James Brass Quintet.