Among his many innovations and timekeeping improvements, Simon Willard is best known for inventing the eight-day patent timepiece that came to be known as the gallery or banjo clock.

The original Willard family had arrived in 1634 from Horsmonden, Kent (England), and they were among the founders of Concord, Massachusetts.

The elder brother, Benjamin, who was 10 years older than Simon, learned horology and opened a workshop adjacent to the house in 1766.

[citation needed] A year later, Benjamin hired an Englishman named Morris to teach horology—particularly to Simon.

Simon and Aaron Willard both combined 18th century knowledge of horology with then-contemporary industrial methods (pre-cast parts, template usage, labor division, standardized production, efficient management).

By 1807, twenty factories in Boston were sub-contracted to supply parts or materials to the Willard brothers' businesses.

This included mahogany (from nearby mills), clock parts (amongst which 20 cabinetmakers were), gilder works, and other important artistic resources.

Indeed, Simon Willard preferred to build sumptuous models that featured elaborate artistic details (especially brass trim).

Simon Willard's clocks required considerable skilled handcraftsmanship, and their movements were outstandingly precise.

His own skills were considerable, and he was able to file cogwheels without leaving file-marks, producing mechanisms with a margin of error of just thirty seconds over the course of a month.

Distinctively for Willard's workshop, above the clock's top fretwork, three pedestals were, on which two spherical finials and a large bird figure were mounted.

In addition, like Aaron, Simon built a glass dial door, whose top had a half arch shape.

Also, with few extra mechanism, amusing wheels with animated figures were featured on the dial, enticing the customer interest effectively.

Additionally, Willard expanded the Banjo clock in accordance with the patent, making much larger "seconds beating" regulators.

It is worth mention, an unusual exemplary displayed in one of the bookshelves of the White House library, made by the clockmaker to commemorate the visit of the Marquis de Lafayette to the United States in 1824-25.

For the United States Capitol in Washington, the Senate requested Simon Willard to build a large gallery clock.

Among their first correspondence, in 1801 Thomas Jefferson alerted Simon Willard that his banjo timepiece hadn't yet been patented.

It was signed by President Jefferson, Secretary of State James Madison, and Attorney General Levi Lincoln.

In subsequent years, Simon Willard visited Thomas Jefferson at his home, Monticello, near Charlottesville, Virginia.

Minister Joseph Eckley and the congregation of Old South Meeting House in Boston, the site of planning for the Boston Tea Party, commissioned Willard to build a carved and gilded gallery clock to hang opposite the pulpit on the balustrade of the room's south gallery.

The clock was delivered c. 1805, and remained within the meeting house until 1872, when the congregation moved to Old South Church in Boston's Back Bay.

A replica has since replaced the original clock within the Old South Meeting House, now a museum on Boston's Freedom Trail.

Many craftsmen had unsuccessfully attempted to repair it, until finally Harvard's authorities offered an important reward to Simon if he was able to fix it.

In 1826, Thomas Jefferson requested that Simon Willard build a clock for the University of Virginia at Charlottesville.

Its mounting was silvered, and it read "Presented by James Madison, Ex-President of the United States, to Simon Willard, May 29, 1827."

After an official request, in 1837 the last two of Simon Willard's important works were again destined for the United States Capitol.

Immediately after arriving to Boston, Willard developed a movable mechanism to turn meat on a spit, the roasting jack, which was specifically designed for outdoor fireplaces.

Beginning in 1828, Simon Willard Jr. (1795–1874) apprenticed in horology at his father's shop; he subsequently established his own workshop in Boston.

On January 24, 2003, with its American Design Series, the US Postal Service issued a commemorative 10 cent stamp which features a Banjo clock, thus remembering Simon Willard.

The stamp — designed by Derry Craig (née Derry Noyes; born 1952 → wife of Washington lawyer Gregory B. Craig) — is a rendering of the dial, or face, of Willard's Banjo Clock, from a watercolor painting by Lou Nolan (né Louis James Nolan; 1926–2008), late of McLean Virginia.