Mural

<spoiler> Hint: "People and dates with lasting effect."

The initials on the mural corespond to the names of the inventors:

EW =Eli Whitney, cotton gin (1793)

HD = Humphrey Davy, an Englishman, demonstrated a powerful electric lamp to the Royal Society in 1806

JW =James Watt, improved steam engine 1763

BF = Benjamin Franklin, pointed light rod conductor

GLL = George Louis Lesage, used a single wire system to telegraph a message (1774)

LP = Louis Pasteur, french scientist who discovered the process of sterilizing milk (1862)

GS = Glenn T. Seaborg, the nuclear chemist's best-known achievement was the synthesis and isolation of the radioactive element plutonium (1941)

GM = Guglielmo Marconi, radio (1897)

AGB = Alexander Graham Bell, inventor of the telephone (1880)

CM = Cyrus Hall McCormick, inventor of the reaper

TE = Thomas Edison, Phonograph

Think JW could also be hydraulic ram invented by John Whitehurst (thanks to confusio)

NOTE: The icons that go with the initials are all the same except for GS and AGB which have an identical icon. </spoiler>