(Reuters) - A shutdown of about a quarter of the U.S. government rolled into its 12th day on Wednesday, with lawmakers and President Donald Trump divided over his demand for money for a border wall.

FILE PHOTO: A sign declares the National Archive is closed due to a partial federal government shutdown in Washington, U.S., December 22, 2018. REUTERS/Joshua Roberts/File Photo/File Photo

The shutdown, which began on Dec. 22, is the 19th to occur since the mid-1970s. Most have been brief. Trump’s latest is the third on the Republican president’s watch and already ranks among the longest ever.

A meeting on the shutdown at the White House with senior lawmakers was scheduled for Wednesday afternoon.

There were several very short shutdowns under Republican President Ronald Reagan. Under Democratic President Bill Clinton, there were two shutdowns, including the longest on record: 21 days in 1996.

A 16-day shutdown happened under Democratic President Barack Obama in 2013 in a fight with Republicans over his healthcare law.

The current shutdown has not affected three-quarters of the government, including the Department of Defense and the Postal Service, which have secure funding. But 800,000 employees from the departments of Homeland Security and Transportation and other agencies have been furloughed or are working without pay.

Here is what is happening around the federal government.

SMITHSONIAN

The Smithsonian museums and the National Zoo in Washington are closed due to the shutdown, according to the Smithsonian website. Among these is the popular National Museum of African American History and Culture, which opened in 2016. “The museum is closed due to the federal government shutdown. Timed entry pass holders will be emailed instructions on how to reschedule their visit,” the museum posted on Instagram.

HOMELAND SECURITY

The department that oversees Customs and Border Protection, Immigration and Customs Enforcement, the Transportation Security Administration, the Coast Guard and the Secret Service is affected. But most employees are “essential,” so they are working without pay until a funding bill is passed.

Of 245,000 agency employees, nearly 213,000 have been deemed “essential,” according to the department’s contingency plan.

HOUSING AND URBAN DEVELOPMENT (HUD)

Most of this department’s 7,500 employees are “non-essential;” only about 340 are working. Nearly 1,000 others may be called in for specific tasks, without pay.

Public housing authorities and Native American tribal housing entities are not part of the federal government and so are not required to shut down. But the federal government provides some of their funding, so they may need to reduce or change operating hours.

HUD, which oversees some housing loan and low-income housing payment programs, warned in its contingency plan that “a protracted shutdown could see a decline in home sales, reversing the trend toward a strengthening market that we’ve been experiencing.”

COMMERCE DEPARTMENT

The Department of Commerce’s Bureau of Economic Analysis and Census Bureau are not publishing economic data, including key figures on gross domestic product, inflation, personal income, spending, trade and new home sales, during the shutdown.

OFFICE OF PERSONNEL MANAGEMENT

The agency that oversees the federal workforce has given advice to workers on dealing with landlords, mortgage lenders and other creditors, including sample letters explaining severe lost income due to the lack of federal funding.

FEDERAL COMMUNICATIONS COMMISSION

The FCC, which regulates radio and television broadcast and cable systems, said it will suspend most operations at midday on Thursday, if the shutdown has not ended by then. Work for “the protection of life and property” will continue. So will operations at the agency’s Office of Inspector General, the FCC’s internal watchdog.

COAST GUARD

Members of the Coast Guard were due to get their final 2018 paychecks on Monday, their last until the government reopens.

FEMA

The Federal Emergency Management Agency (FEMA) was to resume issuing new flood insurance policies during the shutdown, reversing an earlier decision.

INTERIOR

The National Park Service, under the umbrella of the Interior Department, is operating with a skeleton staff. Under its contingency plan, some parks may be accessible, with others closed completely. The National Park Service is providing no visitor services such as restrooms, facility and road maintenance and trash collection.

TRANSPORTATION

Of its 55,000 employees, 20,400 have been put on leave. This excludes most of the Federal Aviation Administration, where 24,200 are working and the Federal Highway Administration, where all 2,700 employees are funded through other sources.

Air traffic control, hazardous material safety inspections and accident investigations continue, but some rulemaking, inspections and audits have been paused.

EXECUTIVE OFFICE OF THE PRESIDENT

An estimated 1,100 of the office’s 1,800 employees are on leave. This includes most of the Office of Management and Budget, which helps implement budget and policy goals.