Americans are deeply divided on many important issues. Too often those differences trigger not just legitimate debate about judgments but ugly assumptions about motives.

Yet our nation still can - and must - rally together in times of crisis. And fresh evidence of such unity was on moving display Tuesday in ceremonies marking the anniversary of a murderous act of mass terror.

On April 15, 2013, two crude bombs exploded about 12 seconds apart near the finish line of the Boston Marathon.

The blasts killed three people - Krystle Campbell, 29; Lingzi Lu, 23; and Martin Richard, 8 - and injured more than 260 others. Three days later, after the authorities identified Dzhokhar and Tamerlan Tsarnaev as suspects, those brothers allegedly killed Massachusetts Institute of Technology police officer Sean Collier, 26. Tarmerlan was then killed in a shootout with law enforcement in Watertown, Mass. Dzhokhar, wounded in that exchange of gunfire, was later taken into custody.

According to the authorities, he identified radical Islamic resentment of the U.S. military interventions in Iraq and Afghanistan as the motive for the bombings, while denying any direct connection to terrorist groups. Dzhokhar Tsarnaev is scheduled to go on trial in November on 30 federal charges. Prosecutors say they will seek the death penalty.

But this verdict on how a great city responded to a devastating challenge came in long ago:

"Boston Strong."

That's the stirring, healing slogan Boston adopted - and has lived up to - while bouncing back from this barbaric outrage.

Even as smoky confusion reigned amid mass carnage a year and a day ago, ordinary folks performed live-saving deeds of extraordinary bravery. Such courage and dedication has continued over the past year as survivors, some of whom suffered life-altering (and limb-losing) damage, have moved forward with bold resolve rather than surrendering to grief, pity and bitterness.

Vice President Joe Biden rightly hailed that shared sense of can-do fortitude at Tuesday's memorial service when he said:

"We are Boston. We are America. We respond. We endure. We overcome. And we own the finish line."

Marathoners will reach that finish line again next Monday. Appropriately enough, the famous race is annually held on the third Monday in April, which in Massachusetts is celebrated as "Patriots' Day" in honor of the Revolutionary War-starting battles of Lexington and Concord on April 19, 1775.

As for the twisted goal behind killing the innocents at last year's marathon:

If the aim was to terrorize Bostonians and indeed, all Americans, it failed.

Instead, that vicious crime galvanized a special city - and an inspired nation - to stand together, "Boston Strong," against the vile forces of terror.