"We took out $1.4740 (in March) and the market took off," said James Quinn, metals analyst with AG Edwards.
Benchmark March copper at the Comex division of the New York Mercantile Exchange settled 4.55 cents, or 3.1 percent, higher at $1.4935 a lb., after hitting a new contract high of $1.5000 in active dealings.
Final volume was estimated at hefty 48,000 lots, the Comex said. Copper futures opened lower but recovered when some local and fund buying emerged in sympathy with firmer overseas markets.
Prices worked higher, building momentum as they pushed through highs from the previous two sessions, analysts said.
Some selling developed at the contract highs, bringing the market off its peak.
Analysts said the late technical rally was underpinned by strong fundamental factors.
China was back in the market, buying after its extended Lunar New Year holiday, and tight market supplies amid seasonal demand and strong aluminium and zinc prices in Europe kept a firm floor under prices.
London Metal Exchange copper stocks fell for the first time in a couple of sessions as warehouse inventories dipped 150 tonnes to 55,950 tonnes on Thursday. Comex stocks were up 500 short tons at 46,527 tons on Wednesday.
Dollar strength undermined copper prices as the greenback firmed following a stronger-than-expected report on jobless claims. Initial US jobless claims for the latest week fell to 302,000, which was lower than economists' forecasts for 315,000.
But the dollar slipped when traders saw nothing new in congressional testimony by Federal Reserve Chairman Alan Greenspan.
His comment that US interest rates remain "fairly low" signalled that further rate hikes lie ahead.
The dollar weakness contributed to copper's gains, making the industrial metal more affordable for overseas investors. Three-month LME copper futures jumped by more than 3 percent to above $3,210 a tonne, a new 16-year peak, on late fund buying on Thursday, traders said.