Question: Bartlett's Bridge was built by the engineer who worked for the county seat of which Massachusetts county?

Context:
Sutliff Bridge
The Sutliff Bridge is a bridge over the Cedar River at Sutliff, a Johnson County community near Lisbon, Iowa, United States.
 A Parker truss bridge, it was built in 1897 and 1898 at a cost of approximately $12,000.
 J.R. Sheely was the engineer for the original Sutliff Bridge.
 After a modern replacement was built over the Cedar in 1983, the bridge was slated for destruction, but it was ultimately saved, and on May 15, 1998, it was added to the National Register of Historic Places.
 Although the bridge remained a celebrated location for locals and for visitors from across Iowa, including a 5k foot race beloved as the “worst road race in America", it succumbed to massive floods in the second week of June 2008: while the river normally flowed many feet below the bottom of the bridge, the floods topped the bridge's deck, and one of the bridge's spans was washed away on June 13 as the surrounding countryside was inundated with vast amounts of water.
 It is estimated that restoring the bridge will cost $1.7 million.
 Most of this money would come from the Federal Emergency Management Agency (FEMA), with the rest coming from donations and local governments; both FEMA and the Johnson County Board of Supervisors have agreed in principle to repair the bridge.
 The bridge reconstruction was supervised by VJ Engineering of Coralville, Iowa and construction was completed by Iowa Bridge and Culvert of Washington, Iowa.
 In October 2012 a ribbon cutting ceremony was held opening the bridge to public use for the first time in four years.
Bartlett's Bridge
Bartlett's Bridge is a historic stone arch bridge carrying Clara Barton Road over the French River in Oxford, Massachusetts.
 The bridge was built in 1889 to a design by Charles A. Allen, at the time a civil engineer for the city of Worcester.
 The bridge was built to replace an older wooden span at the request of Edwin Bartlett, the owner of textile mills in North Oxford, whose businesses and employees would have used the road.
 The bridge is 30 ft long and 42 ft wide, with its elliptical arch reaching a height of 13 ft above the river.
 The facing of the bridge is rough-cut granite that has been fixed with mortar.
 In contrast, the granite stones that make up the arch have been very precisely worked.
 The bridge has parapet walls made of large granite slabs 4.5 ft , 2 ft wide, and 1 ft thick.
Gardnerville Branch Jail
The Gardnerville Branch Jail is a historic jail located at 1440 Courthouse St. in Gardnerville, Nevada.
 The jail was built in 1910 and served as Douglas County's only jail from 1910 to 1915.
 Prior to 1910, the only county jail was in Genoa, the county seat; however, since Gardnerville was several miles from Genoa, it resorted to housing prisoners in the local judge's granary.
 As the granary was considered unfit for holding prisoners, the community petitioned the county to construct a new jail.
 However, local leaders in Minden, who wanted to move the county seat to their town, protested the move, as they suspected that Gardnerville was attempting to claim the county seat itself.
 Nonetheless, the county approved the construction of the new jail.
 The jail housed its first prisoners before construction even finished, as the Genoa jail burned down; one prisoner was briefly chained to a post until the new jail could accommodate him.
 Once completed, the jail served the county until 1915, when Minden became the county seat and opened its own county jail.
Cerro Gordo County Courthouse (Iowa)
The Cerro Gordo County Courthouse is located in Mason City, Iowa, United States.
 When Cerro Gordo County was created in 1855 and Mason City was selected to be the county seat.
 Dissatisfaction in the western part of the county led the Iowa legislature to appoint three new commissioners who would move the county seat to Livonia.
 A courthouse was built there.
 A petition signed by over half of the citizens of the county requested that the county seat be moved back to Mason City.
 Mason City also won the election in 1858 to decide the matter 155-48.
 Two courthouses have stood in Mason City prior to the present Modernist structure that was occupied by the county in 1960.
 It had been built as the Standard Oil Building, and was acquired by the county in 1959 for $159,400 and then remodeled for their use.
Old Allamakee County Courthouse (Lansing, Iowa)
The Old Allamakee County Courthouse, located on 2nd Street in Lansing, is a short-lived former county courthouse of Allamakee County, Iowa.
 The courthouse was completed in 1861 amid a fight between Lansing and Waukon over which community deserved to be the county seat.
 Lansing had lost a vote on the county seat to Waukon in 1859, but they won another vote in 1861 after teaming up with the community of Columbus.
 Waukon built its own courthouse in the meantime, but it failed to win back the county seat in yet another vote in 1864.
 The county sheriff, a Waukon resident, attempted to seize the county's records from the Lansing courthouse in 1866; however, a posse from Lansing stopped him before he could return to Waukon.
 The Iowa Supreme Court decided the county seat battle in favor of Waukon the following year; it has remained there since.
Henry Covered Bridge (Ohio)
The Henry Covered Bridge near Bartlett, Ohio is a historic covered bridge.
 The bridge is on TR61 off OH550 southeast of Bartlett, Ohio, in Washington County, Ohio.
 It is a "Multiple Kingpost" truss type, and it is 45 feet long, and was built in 1894.
Worcester, Massachusetts
Worcester ( , ] ) is a city and the county seat of Worcester County, Massachusetts, United States.
 Named after Worcester, England, as of the 2010 Census the city's population was 181,045, making it the second most populous city in New England after Boston.
 Worcester is located approximately 40 mi west of Boston, 50 mi east of Springfield and 40 mi north of Providence.
 Due to its location in Central Massachusetts, Worcester is known as the "Heart of the Commonwealth", thus, a heart is the official symbol of the city.
 However, the heart symbol may also have its provenance in lore that the mass-produced Valentine's Day card was invented in the city.
Shinn Covered Bridge
The Shinn Covered Bridge is a historic wooden covered bridge in the southeastern part of the U.S. state of Ohio.
 Located in the countryside northeast of Bartlett in Washington County, this single-span truss bridge was built in 1886 by local carpenter Charles T. Shinn.
 Built of weatherboarded walls with stone abutments and a metal roof, the bridge features vertical siding, and its portals have remained vertical and resisted creeping into another shape.
 The heart of the bridge's structure employs the Burr Truss design, which mixes the king post truss with a wooden arch designed by Andrea Palladio in the sixteenth century.
 Shinn built his bridge to span the western branch of Wolf Creek in Palmer Township.
 Measuring 98 ft in length, the bridge was constructed soon after the drowning of one of Shinn's children.
Eisenhower Bridge (Milton, Iowa)
The Eisenhower Bridge is located east of Milton, Iowa, United States.
 It carries traffic on 252nd Street over the Fox River for 197 ft .
 The supervisors from Des Moines and Lee counties met on September 7, 1887 to view the location of a new bridge between the two counties over the Skunk River on the Burlington-Fort Madison Road.
 Financing delayed building the new bridge.
 They determined that Des Moines County would pay three-fifths of the costs and Lee County the remainder.
 Chicago engineer Horace B. Horton designed the Pratt truss, and it was built by the James B. Diver Bridge Company of Keokuk, Iowa.
 The Walker's Ferry Bridge was originally a two-span structure, and it was completed for $9,435.
 It was replaced with another bridge in 1930, and one of the spans was relocated to this location.
 Known locally as the Eisenhower Bridge, it replaced an 1895 span that was washed out in a flood.
 While it lost some of its historical integrity, it remains an example of early wagon bridge construction.
 It is also one of the few iron truss bridges remaining in Iowa, and it was designed by a prominent bridge engineer.
 The bridge was listed on the National Register of Historic Places in 1998.
Main Street Bridge (Charles City, Iowa)
The Main Street Bridge is a historic structure located in Charles City, Iowa, United States.
 It spans the Cedar River for 248 ft .
 Before a bridge was built at this location local citizens would cross the river by way of a ferry, at a ford in summer, and across the ice in winter.
 The first bridge at this location was washed away in a flood while it was under construction in 1858.
 The second bridge was completed in 1864, and it was destroyed in a flood two years later.
 A temporary bridge was completed in 1867, and it was replaced by a truss bridge in 1870.
 It was used for 40 years despite an engineer's study in 1892 that suggested it be condemned.
 The Floyd County Board of Supervisors approved a replacement bridge in 1908.
 The old bridge was moved to a new spot five blocks downstream, but contract problems delayed construction of the new bridge.
 Advance Construction Company of Waukesha, Wisconsin was finally awarded a contract in March 1909.
 The three span concrete filled spandrel arch bridge was designed by their designing engineer G.W. Miller.
 It was completed in 1910 for about $40,000, which was paid for by the county and the city.
 The bridge was listed on the National Register of Historic Places in 1999.

Answer: Worcester County