Poetically, from Associate U.S. Supreme Court Justice Anthony Kennedy:

Here one Latin cross in the desert evokes far more than religion. It evokes thousands of small crosses in foreign fields marking the graves of Americans who fell in battles, battles whose tragedies are compounded if the fallen are forgotten.

And legally:

The goal of avoiding governmental endorsement does not require eradication of all religious symbols in the public realm. A cross by the side of a public highway marking, for instance, the place where a state trooper perished need not be taken as a statement of governmental support for sectarian beliefs. The Constitution does not oblige government to avoid any public acknowledgment of religion's role in society. See Lee v. Weisman, 505 U. S. 577, 598 (1992) ("A relentless and all-pervasive attempt to exclude religion from every aspect of public life could itself become inconsistent with the Constitution"). See also Corporation of Presiding Bishop of Church of Jesus Christ of Latter-day Saints v. Amos, 483 U.S. 327, 334 (1987) ("This Court has long recognized that the government may (and sometimes must) accommodate religious practices and that it may do so without violating the Establishment Clause"). Rather, it leaves room to accommodate divergent values within a constitutionally permissible framework.