Whiteboard
Whiteboards became commercially available in the early 1960s, but did not become widely used until 30 years later. Early whiteboards needed to be wiped with a damp cloth and markers had a tendency to leave marks behind, even after erasing the board. Dry-erase markers for whiteboards were invented in 1975.
Chalkboard eraser
Chalkboard erasers were first invented around 1863 by John L. Hammett, who owned some stores that sold and created school products in Rhode Island and then later in Boston. Mostly slates were sold there as well as chalk and so on. At the time, rags or old cloths were used to erase and get rid of the chalk markings on slates in schools, offices, and for the most part, everywhere. Hammett created the chalkboard before the invention of the chalkboard eraser by creating "slating paint". Hammett then, during a presentation on his chalkboard "discovered" that wool felt strips wiped off the chalk writing better than rags. Following this discovery he gathered a team to create the custom eraser for sale. The erasers proved to be a success for Hammett and, later in the 19th century, he created a company that also sold inexpensive supplies for teachers and schools, such as paper, ink, etc. Hammett ultimately sold the company.