Bishop McGann-Mercy Diocesan High School

Suffolk County () is the easternmost county in the U.S. state of New York. It comprises the eastern two-thirds of Long Island, bordered to its west by Nassau County, to its east by Gardiners Bay and the Atlantic Ocean, to its north by Long Island Sound, and to its south by Great South Bay. As of the 2020 United States census, the county's population was 1,525,920, its highest decennial count ever, making Suffolk the fourth-most populous county in the State of New York, or the most populous if the New York City boroughs are not considered counties. Its county seat is Riverhead, though most county offices are in Hauppauge. The county was named after the county of Suffolk in England, the origin of its earliest European settlers. Suffolk County incorporates the easternmost extreme of the New York City metropolitan area. The geographically largest of Long Island's four counties and the second-largest of New York state's 62 counties, Suffolk County is 86 miles (138 km) in length and 26 miles (42 km) in width at its widest (including water). Most of the island is near sea level, with over 1,000 miles of coastline.Like other parts of Long Island, the county's high population density and proximity to New York City has resulted in a diverse economy, including industry, science, agriculture, fishery, and tourism. Major scientific research facilities in Suffolk County include Brookhaven National Laboratory in Upton, Cold Spring Harbor Laboratory in Huntington, and Plum Island Animal Disease Center on Plum Island. The county is home to Stony Brook University in Stony Brook and Farmingdale State College in Farmingdale.

Riverhead is a town in Suffolk County, New York, United States, on the north shore of Long Island. Since 1727, Riverhead has been the county seat of Suffolk County, though most county offices are in Hauppauge. As of the 2020 census, the population was 35,902. The town rests on the mouth of the Peconic River, from which it derives its name. The smaller hamlet of Riverhead lies within it, and is the town's principal economic center. The town is 166 miles (267 km) southwest of Boston via the Orient Point-New London Ferry, and is 76 miles (123 km) northeast of New York City. In the beginning of the 20th century, the town saw an influx of Polish immigrants. This led to the creation of Polish Town, a section of the Town and County seat where the popular Polish Town Fair is held annually.Riverhead is the agricultural apex of Long Island, with 20,000 of the 35,000 acres of the island's farmland located within the town. The town is also home to four separate beaches which are open year round. Iron Pier, Wading River, and Reeves Beach each offer boating access for residents and visitors alike.

Riverhead is a census-designated place (CDP) roughly corresponding to the hamlet by the same name located in the Town of Riverhead in Suffolk County, on Long Island, in New York, United States. The CDP's population was 13,299 at the 2010 census.Situated at the mouth of the Peconic River, which empties into Peconic Bay where the North and South Forks of Long Island split, the town of Riverhead (of which the CDP is a part) is the official county seat of Suffolk County. In the 1960s, most of the county offices moved to the CDP of Hauppauge in the towns of Islip and Smithtown in the more populous western half of the county—a move which still spurs attempts for the town of Riverhead to lead the way for the secession of eastern Long Island towns to form Peconic County.

The Railroad Museum of Long Island is a railway museum based on the North Fork, of Long Island, New York, in the United States. It has two locations, the main location in Riverhead, and a satellite location in Greenport, west of the North Ferry to Shelter Island. Both facilities contain active model railroad displays and gift shops.

Riverhead is a station along the Main Line (Greenport Branch) of the Long Island Rail Road. It is located on Osborne Avenue and Railroad Street in Riverhead, New York, north of NY 25 (West Main Street) and the Suffolk County Court House.

Suffolk County Historical Society Building is a museum and library dedicated to preserving historic artifacts of Suffolk County, New York, as well as other parts of Long Island. It is located at 300 West Main Street as well as Osborn Avenue and Court Street in Riverhead, New York. Though the museum building itself has only been around since 1930, the Suffolk County Historical Society was established in 1886 by residents of the county who were concerned about preserving its heritage. Riverhead was chosen as the location of the new society because it's the County Seat of Suffolk County, and County Surrogate Judge James H. Tuthill became the first President. The society began collecting items almost immediately, and the first displays were placed in a small glass case in Tuthill's Riverhead office. Unfortunately, the collection soon outgrew the Judge's office, and in 1893 a small building at the corner of Griffing Avenue and Main Street in Riverhead, which formerly housed the County Clerk's Office, was purchased. Eventually, the growing collection of documents and artifacts outgrew that space too. The building was designed by August Galow with Colonial Revival styling. It was built on land donated by Alice O. Perkins, the widow of prominent Riverhead resident John Perkins during the 1920s, and was completed in 1930. Extensions were added in 1951 and 1964. The library boasts more than 20,000 volumes and over 840 cubic feet (24 m3) of manuscripts, including records, ledgers, diaries, maps, atlases, post cards, newspapers, and other paperwork. In 1994, the building was listed on the National Register of Historic Places.

Riverhead Post Office is a United States post office located at 1210 West Main Street in Riverhead, New York. It serves the ZIP code 11901, covering all of Riverhead, along with Roanoke, Reeves Park, Centerville, northern Jamesport, and northwestern Laurel.The old Riverhead Post Office was designed by Louis A. Simon who was Supervising Architect for the United States Treasury Department. Simon also designed the Post Office buildings in Bay Shore, Northport, and Westhampton Beach. According to the Riverhead Town Historian, the land for the Post Office was purchased in 1932, with the building erected in 1935 and dedicated in November of that year. The post office was a depression-era public works project. It is built in a simplified Colonial Revival style.As with Patchogue and Smithtown's Village of the Branch, Riverhead Post Office was known as a source for obscure postal denominations by Long Island-based stamp collectors. The building was added to the National Register of Historic Places in 1989.

The Vail-Leavitt Music Hall is a late nineteenth-century theater presently in use on the east end of Long island in Riverhead, New York. The building was built by David F. Vail, with the help of his son George M. Vail in 1881. David was a local lumber dealer in the Riverhead and Eastern Suffolk County Long Island area. The theater/music hall opened on October 11, 1881. The main theater and its balcony are a miniature opera house designed by J. W. Flack. The ground floor of the building housed commercial business storefronts, while the upstairs contained the opera house. The music hall began its operations with candle lighting, however the Vail's began operating a gas plant behind the theater. As a result, gas fixtures were placed all along the horseshoe balcony, and gaslight continued at the music hall until the advent of electricity to the area in July 1888, when the venue added electric lights. In 1908, George M. Vail, now sole owner of Music Hall, sold the building to Simon Leavitt, a tailor and clothier, who leased out the upstairs as a theatrical venue. In 1914, the Music Hall was used by Thomas Edison as a demonstration site for kinetophone, an early attempt at the synchronization of sound and film. As more modern theaters were built in the area, the Music Hall was converted for use over the years as a restaurant, a roller skating rink and even a betting parlor. However, the balcony and stage proscenium remained intact throughout the conversions. Eventually Theodore Leavitt (Simon's son) took over the clothier business and closed the upstairs, using it only as a storage area until his retirement in the 1970s.After his death, Theodore Leavitt's widow Mollie Leavitt owned the music hall until its acquisition by the Council for the Vail-Leavitt Music Hall in 1982 through a grant from the U.S. Department of Housing and Urban Development arranged by the Town of Riverhead's Community Development officer, Robert Schemer. The Council is a not-for-profit 501(c)3 charitable corporation which now oversees and operates the venue. From the early eighties to the late nineties, old movies were shown on a small screen in its downstairs space, dubbed the "Mini-Cine". These movie showings helped the theater raise monies for the music hall's restoration. The theater has been listed on the National Register of Historic Places since August 25, 1983. The music hall held its grand re-opening on June 28, 2003. It continues to host numerous cultural, civic and charitable events throughout the year for the local community.

Long Island Aquarium (formerly Atlantis Marine World) is an aquarium that opened in 2000 on Long Island in Riverhead, New York, United States. One of its biggest attractions is a 20,000-US-gallon (76,000 L) coral reef display tank, which is one of the largest all-living coral displays in the Western Hemisphere.

The Peconic River is a river within Suffolk County on Long Island, New York. The river is located in the eastern end of Long Island. The Peconic River drains an area between the Harbor Hill Moraine and flows into Flanders Bay, which in turn connects to Peconic Bay east of Riverhead. The river originates in bogs and wetlands in central Long Island near the Brookhaven National Laboratory and flows eastward to the Peconic Bay. It is the longest river on Long Island and is almost entirely within the Central Long Island Pine Barrens which was set up in 1993 to protect its relative wilderness standing. It is fresh water until about the center of Riverhead where it becomes an estuary. The river is slow-moving, making it ideal for canoeing and kayaking. It forms the border between Brookhaven and Riverhead towns as well as the border between Riverhead and Southampton.

WRIV (1390 AM) is a radio station licensed to Riverhead, New York. Established in 1955, the station broadcasts an adult standards format to eastern Long Island. The station, which has been owned since 1987 by Crystal Coast Communications, has daytime power of 1,000 watts and 64 watts at night.

WFTU (1570 AM) is a college radio station owned and operated by Five Towns College and licensed to Riverhead, New York. It broadcasts a variety format featuring programming produced by current students and faculty of Five Towns College. The station is also operated by a student management staff under the guidance of the general manager, a staff professor. The studio is located on the campus in Dix Hills, New York and transmitter is in Riverside, New York. The station also streams on the internet from its website.