The data for 2010 shows that while New Jersey remains the most densely populated in the country, it grew at a less robust pace than most other states. It is currently the country's 11th most populated state with 8.8 million residents, slipping two notches from 9th place in 2000 even after gaining 400,000 residents in the past 10 years.
For Pennsylvania, it is the smallest reduction in its delegation in seven decades.
Reapportionment figures cut the number of congressmen from the state from 19 to 18, despite Pennsylvania's total population growing slightly over the past decade, from 12.3 million to 12.7 million. The state's growth rate of 3.4 percent lagged far behind the national rate of 12.7 percent.
The loss of a seat also means there will be one less lawmaker in Washington advocating for a return of federal dollars to New Jersey, said Assemblyman John Wisniewski, who heads the Democratic State Committee.
"It means a smaller voice in national affairs," Ernest Reock, a professor emeritus at the Center for Government Services at Rutgers University and a former redistricting committee staff member, said when asked to sum up the effect on Garden State voters.
Congressional districts that will be newly drawn next year will each contain 710,000 residents, about 60,000 more people than each district now in New Jersey.
The loss of only one seat is the fewest Pennsylvania has shed since 1940, when the number also fell by one, to 33. There were 36 Pennsylvania congressmen in the 1910s and 1920s.
In every other census since 1950, Pennsylvania has lost either two or three of its representatives in Washington.
New Jersey's downward trend began 30 years ago when the Garden State lost its 15th congressional seat. New Jersey also lost a seat after 1990 count, but the number of congressional districts remained unchanged in 2000.
The shift means one fewer electoral vote for New Jersey - 14 instead of the current 15 - making the state "an incrementally smaller prize for presidential candidates," said Wisniewski, who is on the legislative redistricting panel.
The states are two of eight set to lose one seat in Congress. Others include Massachusetts. Two other states, Ohio and New York, will each lose two seats. The big winners were Texas, which gained four seats, and Florida, which gained two.
The numbers will trigger a high-stakes process where the dominant party in each state gets the chance to redraw the election map, shaping the political landscape for the next 10 years.
In New Jersey, a bipartisan commission is assigned to do the redistricting. Republicans and Democrats are already meeting to determine how the new congressional districts will be drawn.
Nonetheless, Republican Gov. Chris Christie on Tuesday predicted a partisan squabble.
"It'll be intensely partisan because someone's going to lose a seat," Christie said after signing a bill capping arbitration awards in Wayne. "The Democrats will want the Republicans to lose a seat and the Republicans will want the Democrats to lose a seat. There'll also be elements of fact that will hopefully be injected into it regarding where the population growth has been and what are appropriate ways to draw districts."
Pennsylvania's state Legislature and governor will have to decide over the coming year how to redraw the lines of the state's congressional districts, a process that will require precinct-level population figures that are not expected to be released for several months.
Population estimates issued over the past decade indicate the state's western region has shed population, while southeastern areas - Chester County in particular - have experienced gains. That suggests the new congressional district map may consolidate two western districts. That decision will rest with the state House, Senate and governor, which will all be in Republican hands next year.
Drawing new district lines for the Pa. state House and Senate proceeds on a separate and much different track. Tuesday's release by the Census Bureau starts the clock ticking on that timeline.
The current makeup of New Jersey's congressional delegation is eight Democrats and five Republicans; when the new Congress is sworn in next month, it will have seven Democrats and six Republicans. Both the state's U.S. senators are Democrats.
The map as currently drawn is heavily Republican or heavily Democratic, depending on the district, which results in few competitive congressional races. That was done intentionally and with the agreement of the incumbent congressmen, said Reock.
The new map, however it is redrawn, will push two incumbents into a competitive re-election face-off in a newly drawn district unless at least one New Jersey representative decides not to run again.
The next congressional elections are in 2012.
Associated Press reporter David Porter in Wayne contributed to this report.